From 7ea37342408df46b9005560235fbcb7eac8bcdd9 Mon Sep 17 00:00:00 2001
From: vvakame <vvakame+dev@gmail.com>
Date: Fri, 25 Nov 2016 13:45:37 +0900
Subject: [PATCH] address feedback

---
 src/compiler/transformers/es2015.ts           |   6 +-
 ...sClassHeritageListMemberTypeAnnotations.js |   6 +-
 ...accessibleTypeInTypeParameterConstraint.js |   6 +-
 .../reference/abstractClassInLocalScope.js    |   6 +-
 .../abstractClassInLocalScopeIsAbstract.js    |   6 +-
 tests/baselines/reference/abstractProperty.js |   6 +-
 .../reference/abstractPropertyNegative.js     |   6 +-
 .../accessOverriddenBaseClassMember1.js       |   6 +-
 .../accessors_spec_section-4.5_inference.js   |   6 +-
 .../reference/aliasUsageInAccessorsOfClass.js |   6 +-
 .../baselines/reference/aliasUsageInArray.js  |   6 +-
 .../aliasUsageInFunctionExpression.js         |   6 +-
 .../reference/aliasUsageInGenericFunction.js  |   6 +-
 .../reference/aliasUsageInIndexerOfClass.js   |   6 +-
 .../reference/aliasUsageInObjectLiteral.js    |   6 +-
 .../reference/aliasUsageInOrExpression.js     |   6 +-
 ...aliasUsageInTypeArgumentOfExtendsClause.js |  12 +-
 .../reference/aliasUsageInVarAssignment.js    |   6 +-
 .../reference/ambiguousOverloadResolution.js  |   6 +-
 .../reference/apparentTypeSubtyping.js        |   6 +-
 .../reference/apparentTypeSupertype.js        |   6 +-
 .../reference/arrayAssignmentTest1.js         |   6 +-
 .../reference/arrayAssignmentTest2.js         |   6 +-
 .../reference/arrayBestCommonTypes.js         |   6 +-
 .../reference/arrayLiteralTypeInference.js    |   6 +-
 tests/baselines/reference/arrayLiterals.js    |   6 +-
 .../arrayLiteralsWithRecursiveGenerics.js     |   6 +-
 ...rayOfSubtypeIsAssignableToReadonlyArray.js |   6 +-
 .../reference/arrowFunctionContexts.js        |   6 +-
 .../assignmentCompatWithCallSignatures3.js    |   6 +-
 .../assignmentCompatWithCallSignatures4.js    |   6 +-
 .../assignmentCompatWithCallSignatures5.js    |   6 +-
 .../assignmentCompatWithCallSignatures6.js    |   6 +-
 ...ssignmentCompatWithConstructSignatures3.js |   6 +-
 ...ssignmentCompatWithConstructSignatures4.js |   6 +-
 ...ssignmentCompatWithConstructSignatures5.js |   6 +-
 ...ssignmentCompatWithConstructSignatures6.js |   6 +-
 .../assignmentCompatWithNumericIndexer.js     |   6 +-
 .../assignmentCompatWithNumericIndexer3.js    |   6 +-
 .../assignmentCompatWithObjectMembers4.js     |   6 +-
 ...nmentCompatWithObjectMembersOptionality.js |   6 +-
 ...mentCompatWithObjectMembersOptionality2.js |   6 +-
 .../assignmentCompatWithStringIndexer.js      |   6 +-
 .../reference/assignmentLHSIsValue.js         |   6 +-
 .../reference/asyncImportedPromise_es5.js     |   6 +-
 tests/baselines/reference/autolift4.js        |   6 +-
 tests/baselines/reference/baseCheck.js        |   6 +-
 .../reference/baseIndexSignatureResolution.js |   6 +-
 .../reference/baseTypeOrderChecking.js        |   6 +-
 .../baseTypeWrappingInstantiationChain.js     |   6 +-
 tests/baselines/reference/bases.js            |   6 +-
 .../bestCommonTypeOfConditionalExpressions.js |   6 +-
 ...bestCommonTypeOfConditionalExpressions2.js |   6 +-
 .../reference/bestCommonTypeOfTuple2.js       |   6 +-
 ...allSignatureAssignabilityInInheritance2.js |   6 +-
 ...allSignatureAssignabilityInInheritance3.js |   6 +-
 ...allSignatureAssignabilityInInheritance4.js |   6 +-
 ...allSignatureAssignabilityInInheritance5.js |   6 +-
 ...allSignatureAssignabilityInInheritance6.js |   6 +-
 tests/baselines/reference/callWithSpread.js   |   6 +-
 .../reference/captureThisInSuperCall.js       |   6 +-
 tests/baselines/reference/castingTuple.js     |   6 +-
 .../baselines/reference/chainedAssignment3.js |   6 +-
 ...arameterConstrainedToOtherTypeParameter.js |   6 +-
 .../reference/checkForObjectTooStrict.js      |   6 +-
 .../checkSuperCallBeforeThisAccessing1.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing2.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing3.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing4.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing5.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing6.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing7.js     |   6 +-
 .../checkSuperCallBeforeThisAccessing8.js     |   6 +-
 .../reference/circularImportAlias.js          |   6 +-
 .../circularTypeofWithFunctionModule.js       |   6 +-
 .../classAbstractConstructorAssignability.js  |   6 +-
 .../reference/classAbstractCrashedOnce.js     |   6 +-
 .../reference/classAbstractExtends.js         |   6 +-
 .../reference/classAbstractFactoryFunction.js |   6 +-
 .../reference/classAbstractGeneric.js         |   6 +-
 .../reference/classAbstractInAModule.js       |   6 +-
 .../reference/classAbstractInheritance.js     |   6 +-
 .../reference/classAbstractInstantiations1.js |   6 +-
 .../reference/classAbstractInstantiations2.js |   6 +-
 .../classAbstractOverrideWithAbstract.js      |   6 +-
 .../reference/classAbstractSuperCalls.js      |   6 +-
 .../classAbstractUsingAbstractMethod1.js      |   6 +-
 .../classAbstractUsingAbstractMethods2.js     |   6 +-
 .../classConstructorAccessibility2.js         |   6 +-
 .../classConstructorAccessibility4.js         |   6 +-
 .../classConstructorAccessibility5.js         |   6 +-
 ...classConstructorParametersAccessibility.js |   6 +-
 ...lassConstructorParametersAccessibility2.js |   6 +-
 ...lassConstructorParametersAccessibility3.js |   6 +-
 ...clarationMergedInModuleWithContinuation.js |   6 +-
 .../classDeclaredBeforeClassFactory.js        |   6 +-
 .../classDoesNotDependOnBaseTypes.js          |   6 +-
 tests/baselines/reference/classExpression2.js |   6 +-
 tests/baselines/reference/classExpression3.js |   6 +-
 .../classExpressionExtendingAbstractClass.js  |   6 +-
 .../reference/classExtendingBuiltinType.js    |   6 +-
 .../reference/classExtendingClass.js          |   6 +-
 .../reference/classExtendingClassLikeType.js  |   6 +-
 .../reference/classExtendingNonConstructor.js |   6 +-
 .../baselines/reference/classExtendingNull.js |   6 +-
 .../reference/classExtendingPrimitive.js      |   6 +-
 .../reference/classExtendingPrimitive2.js     |   6 +-
 .../reference/classExtendingQualifiedName.js  |   6 +-
 .../reference/classExtendingQualifiedName2.js |   6 +-
 .../reference/classExtendsAcrossFiles.js      |  12 +-
 ...sMergedWithModuleNotReferingConstructor.js |   6 +-
 ...tendsClauseClassNotReferringConstructor.js |   6 +-
 .../reference/classExtendsEveryObjectType.js  |   6 +-
 .../reference/classExtendsEveryObjectType2.js |   6 +-
 .../reference/classExtendsInterface.js        |   6 +-
 .../classExtendsInterfaceInExpression.js      |   6 +-
 .../classExtendsInterfaceInModule.js          |   6 +-
 .../baselines/reference/classExtendsItself.js |   6 +-
 .../reference/classExtendsItselfIndirectly.js |   6 +-
 .../classExtendsItselfIndirectly2.js          |   6 +-
 .../classExtendsItselfIndirectly3.js          |  36 +-
 .../classExtendsMultipleBaseClasses.js        |   6 +-
 tests/baselines/reference/classExtendsNull.js |   6 +-
 ...classExtendsShadowedConstructorFunction.js |   6 +-
 .../classExtendsValidConstructorFunction.js   |   6 +-
 .../classHeritageWithTrailingSeparator.js     |   6 +-
 .../reference/classImplementsClass2.js        |   6 +-
 .../reference/classImplementsClass3.js        |   6 +-
 .../reference/classImplementsClass4.js        |   6 +-
 .../reference/classImplementsClass5.js        |   6 +-
 .../reference/classImplementsClass6.js        |   6 +-
 tests/baselines/reference/classIndexer3.js    |   6 +-
 tests/baselines/reference/classInheritence.js |   6 +-
 .../reference/classIsSubtypeOfBaseType.js     |   6 +-
 tests/baselines/reference/classOrder2.js      |   6 +-
 tests/baselines/reference/classOrderBug.js    |   6 +-
 .../reference/classSideInheritance1.js        |   6 +-
 .../reference/classSideInheritance2.js        |   6 +-
 .../reference/classSideInheritance3.js        |   6 +-
 tests/baselines/reference/classUpdateTests.js |   6 +-
 .../classWithBaseClassButNoConstructor.js     |   6 +-
 .../reference/classWithConstructors.js        |   6 +-
 .../reference/classWithProtectedProperty.js   |   6 +-
 .../reference/classWithStaticMembers.js       |   6 +-
 tests/baselines/reference/classdecl.js        |   6 +-
 .../reference/clodulesDerivedClasses.js       |   6 +-
 ...llisionSuperAndLocalFunctionInAccessors.js |   6 +-
 ...isionSuperAndLocalFunctionInConstructor.js |   6 +-
 .../collisionSuperAndLocalFunctionInMethod.js |   6 +-
 ...ollisionSuperAndLocalFunctionInProperty.js |   6 +-
 .../collisionSuperAndLocalVarInAccessors.js   |   6 +-
 .../collisionSuperAndLocalVarInConstructor.js |   6 +-
 .../collisionSuperAndLocalVarInMethod.js      |   6 +-
 .../collisionSuperAndLocalVarInProperty.js    |   6 +-
 .../collisionSuperAndNameResolution.js        |   6 +-
 .../reference/collisionSuperAndParameter.js   |   6 +-
 .../reference/collisionSuperAndParameter1.js  |   6 +-
 ...perAndPropertyNameAsConstuctorParameter.js |   6 +-
 ...xpressionAndLocalVarWithSuperExperssion.js |   6 +-
 .../reference/commentsInheritance.js          |   6 +-
 .../comparisonOperatorWithIdenticalObjects.js |   6 +-
 ...ithNoRelationshipObjectsOnCallSignature.js |   6 +-
 ...lationshipObjectsOnConstructorSignature.js |   6 +-
 ...thNoRelationshipObjectsOnIndexSignature.js |   6 +-
 ...nshipObjectsOnInstantiatedCallSignature.js |   6 +-
 ...jectsOnInstantiatedConstructorSignature.js |   6 +-
 ...peratorWithSubtypeObjectOnCallSignature.js |   6 +-
 ...WithSubtypeObjectOnConstructorSignature.js |   6 +-
 ...eratorWithSubtypeObjectOnIndexSignature.js |   6 +-
 ...ubtypeObjectOnInstantiatedCallSignature.js |   6 +-
 ...bjectOnInstantiatedConstructorSignature.js |   6 +-
 ...isonOperatorWithSubtypeObjectOnProperty.js |   6 +-
 .../reference/complexClassRelationships.js    |   6 +-
 ...catedGenericRecursiveBaseClassReference.js |   6 +-
 .../reference/compoundAssignmentLHSIsValue.js |   6 +-
 ...poundExponentiationAssignmentLHSIsValue.js |   6 +-
 .../reference/computedPropertyNames24_ES5.js  |   6 +-
 .../reference/computedPropertyNames25_ES5.js  |   6 +-
 .../reference/computedPropertyNames26_ES5.js  |   6 +-
 .../reference/computedPropertyNames27_ES5.js  |   6 +-
 .../reference/computedPropertyNames28_ES5.js  |   6 +-
 .../reference/computedPropertyNames30_ES5.js  |   6 +-
 .../reference/computedPropertyNames31_ES5.js  |   6 +-
 .../reference/computedPropertyNames43_ES5.js  |   6 +-
 .../reference/computedPropertyNames44_ES5.js  |   6 +-
 .../reference/computedPropertyNames45_ES5.js  |   6 +-
 .../conditionalOperatorWithIdenticalBCT.js    |   6 +-
 .../conditionalOperatorWithoutIdenticalBCT.js |   6 +-
 .../reference/constantOverloadFunction.js     |   6 +-
 .../constantOverloadFunctionNoSubtypeError.js |   6 +-
 ...nstraintCheckInGenericBaseTypeReference.js |   6 +-
 ...uctSignatureAssignabilityInInheritance2.js |   6 +-
 ...uctSignatureAssignabilityInInheritance3.js |   6 +-
 ...uctSignatureAssignabilityInInheritance4.js |   6 +-
 ...uctSignatureAssignabilityInInheritance5.js |   6 +-
 ...uctSignatureAssignabilityInInheritance6.js |   6 +-
 tests/baselines/reference/constructorArgs.js  |   6 +-
 ...uctorFunctionTypeIsAssignableToBaseType.js |   6 +-
 ...ctorFunctionTypeIsAssignableToBaseType2.js |   6 +-
 .../constructorHasPrototypeProperty.js        |   6 +-
 .../reference/constructorOverloads2.js        |   6 +-
 .../reference/constructorOverloads3.js        |   6 +-
 .../reference/constructorWithCapturedSuper.js |   6 +-
 ...constructorWithIncompleteTypeAnnotation.js |   6 +-
 .../contextualTypingArrayOfLambdas.js         |   6 +-
 ...contextualTypingOfConditionalExpression.js |   6 +-
 ...ontextualTypingOfConditionalExpression2.js |   6 +-
 ...urcePropertyIsRelatableToTargetProperty.js |   6 +-
 .../reference/declFileClassExtendsNull.js     |   6 +-
 .../declFileForFunctionTypeAsTypeParameter.js |   6 +-
 ...ileGenericClassWithGenericExtendedClass.js |   6 +-
 .../reference/declFileGenericType.js          |   6 +-
 .../reference/declFileGenericType2.js         |   6 +-
 ...lictingWithClassReferredByExtendsClause.js |   6 +-
 ...dsClauseThatHasItsContainerNameConflict.js |   6 +-
 .../declarationEmitExpressionInExtends.js     |   6 +-
 .../declarationEmitExpressionInExtends2.js    |   6 +-
 .../declarationEmitExpressionInExtends3.js    |   6 +-
 .../declarationEmitExpressionInExtends4.js    |   6 +-
 .../declarationEmitNameConflicts3.js          |   6 +-
 .../declarationEmitProtectedMembers.js        |   6 +-
 .../declarationEmitThisPredicates01.js        |   6 +-
 ...tionEmitThisPredicatesWithPrivateName01.js |   6 +-
 .../reference/declareDottedExtend.js          |   6 +-
 .../reference/decoratorOnClassConstructor2.js |   6 +-
 .../reference/decoratorOnClassConstructor3.js |   6 +-
 .../reference/decoratorOnClassMethod12.js     |   6 +-
 ...edClassConstructorWithExplicitReturns01.js |   6 +-
 ...assConstructorWithExplicitReturns01.js.map |   2 +-
 ...tructorWithExplicitReturns01.sourcemap.txt | 268 +++---
 ...derivedClassConstructorWithoutSuperCall.js |   6 +-
 ...ClassFunctionOverridesBaseClassAccessor.js |   6 +-
 .../derivedClassIncludesInheritedMembers.js   |   6 +-
 ...idesIndexersWithAssignmentCompatibility.js |   6 +-
 .../derivedClassOverridesPrivateFunction1.js  |   6 +-
 .../derivedClassOverridesPrivates.js          |   6 +-
 .../derivedClassOverridesProtectedMembers.js  |   6 +-
 .../derivedClassOverridesProtectedMembers2.js |   6 +-
 .../derivedClassOverridesProtectedMembers3.js |   6 +-
 .../derivedClassOverridesProtectedMembers4.js |   6 +-
 .../derivedClassOverridesPublicMembers.js     |   6 +-
 .../derivedClassOverridesWithoutSubtype.js    |   6 +-
 .../derivedClassParameterProperties.js        |   6 +-
 ...dClassSuperCallsInNonConstructorMembers.js |   6 +-
 .../derivedClassSuperCallsWithThisArg.js      |   6 +-
 .../reference/derivedClassTransitivity.js     |   6 +-
 .../reference/derivedClassTransitivity2.js    |   6 +-
 .../reference/derivedClassTransitivity3.js    |   6 +-
 .../reference/derivedClassTransitivity4.js    |   6 +-
 .../reference/derivedClassWithAny.js          |   6 +-
 ...ivateInstanceShadowingProtectedInstance.js |   6 +-
 ...hPrivateInstanceShadowingPublicInstance.js |   6 +-
 ...thPrivateStaticShadowingProtectedStatic.js |   6 +-
 ...sWithPrivateStaticShadowingPublicStatic.js |   6 +-
 .../derivedClassWithoutExplicitConstructor.js |   6 +-
 ...derivedClassWithoutExplicitConstructor2.js |   6 +-
 ...derivedClassWithoutExplicitConstructor3.js |   6 +-
 tests/baselines/reference/derivedClasses.js   |   6 +-
 .../reference/derivedGenericClassWithAny.js   |   6 +-
 ...sesHiddenBaseCallViaSuperPropertyAccess.js |   6 +-
 .../derivedTypeDoesNotRequireExtendsClause.js |   6 +-
 .../destructuringParameterDeclaration5.js     |   6 +-
 ...BeforeEmitParameterPropertyDeclaration1.js |   6 +-
 ...SuperCallBeforeEmitPropertyDeclaration1.js |   6 +-
 ...arationAndParameterPropertyDeclaration1.js |   6 +-
 .../reference/emitThisInSuperMethodCall.js    |   6 +-
 tests/baselines/reference/emptyModuleName.js  |   6 +-
 ...rorForwardReferenceForwadingConstructor.js |   6 +-
 tests/baselines/reference/errorSuperCalls.js  |   6 +-
 .../reference/errorSuperPropertyAccess.js     |   6 +-
 .../reference/errorsInGenericTypeReference.js |   6 +-
 .../reference/es6ClassSuperCodegenBug.js      |   6 +-
 tests/baselines/reference/es6ClassTest.js     |   6 +-
 tests/baselines/reference/es6ClassTest2.js    |   6 +-
 tests/baselines/reference/es6ClassTest7.js    |   6 +-
 .../exportAssignmentOfGenericType1.js         |   6 +-
 .../exportDeclarationInInternalModule.js      |   6 +-
 tests/baselines/reference/extBaseClass1.js    |   6 +-
 tests/baselines/reference/extBaseClass2.js    |   6 +-
 .../extendAndImplementTheSameBaseType.js      |   6 +-
 .../extendAndImplementTheSameBaseType2.js     |   6 +-
 .../extendBaseClassBeforeItsDeclared.js       |   6 +-
 .../extendClassExpressionFromModule.js        |   6 +-
 .../extendConstructSignatureInInterface.js    |   6 +-
 .../reference/extendNonClassSymbol1.js        |   6 +-
 .../reference/extendNonClassSymbol2.js        |   6 +-
 .../extendPrivateConstructorClass.js          |   6 +-
 ...xtendingClassFromAliasAndUsageInIndexer.js |  12 +-
 .../reference/extendsClauseAlreadySeen.js     |   6 +-
 .../reference/extendsClauseAlreadySeen2.js    |   6 +-
 tests/baselines/reference/fluentClasses.js    |   6 +-
 tests/baselines/reference/for-inStatements.js |   6 +-
 .../reference/for-inStatementsInvalid.js      |   6 +-
 .../forStatementsMultipleInvalidDecl.js       |   6 +-
 .../reference/functionImplementationErrors.js |   6 +-
 .../reference/functionImplementations.js      |   6 +-
 .../reference/functionSubtypingOfVarArgs.js   |   6 +-
 .../reference/functionSubtypingOfVarArgs2.js  |   6 +-
 .../reference/generatedContextualTyping.js    |   6 +-
 .../genericBaseClassLiteralProperty.js        |   6 +-
 .../genericBaseClassLiteralProperty2.js       |   6 +-
 ...allWithConstraintsTypeArgumentInference.js |   6 +-
 .../genericCallWithObjectTypeArgs2.js         |   6 +-
 ...icCallWithObjectTypeArgsAndConstraints2.js |   6 +-
 ...icCallWithObjectTypeArgsAndConstraints3.js |   6 +-
 .../genericCallbacksAndClassHierarchy.js      |   6 +-
 .../genericClassExpressionInFunction.js       |   6 +-
 ...sInheritsConstructorFromNonGenericClass.js |   6 +-
 ...cClassPropertyInheritanceSpecialization.js |   6 +-
 .../reference/genericClassStaticMethod.js     |   6 +-
 tests/baselines/reference/genericClasses3.js  |   6 +-
 ...genericConstraintOnExtendedBuiltinTypes.js |   6 +-
 ...enericConstraintOnExtendedBuiltinTypes2.js |   6 +-
 .../genericDerivedTypeWithSpecializedBase.js  |   6 +-
 .../genericDerivedTypeWithSpecializedBase2.js |   6 +-
 .../genericInheritedDefaultConstructors.js    |   6 +-
 .../reference/genericPrototypeProperty2.js    |   6 +-
 .../reference/genericPrototypeProperty3.js    |   6 +-
 ...ericRecursiveImplicitConstructorErrors2.js |   6 +-
 ...ericRecursiveImplicitConstructorErrors3.js |   6 +-
 .../reference/genericTypeAssertions2.js       |   6 +-
 .../reference/genericTypeAssertions4.js       |   6 +-
 .../reference/genericTypeAssertions6.js       |   6 +-
 .../reference/genericTypeConstraints.js       |   6 +-
 ...genericTypeReferenceWithoutTypeArgument.js |   6 +-
 ...enericTypeReferenceWithoutTypeArgument2.js |   6 +-
 .../genericWithIndexerOfTypeParameterType2.js |   6 +-
 .../reference/heterogeneousArrayLiterals.js   |   6 +-
 .../reference/ifDoWhileStatements.js          |   6 +-
 .../illegalSuperCallsInConstructor.js         |   6 +-
 .../implementClausePrecedingExtends.js        |   6 +-
 ...gAnInterfaceExtendingClassWithPrivates2.js |   6 +-
 ...AnInterfaceExtendingClassWithProtecteds.js |   6 +-
 .../baselines/reference/importAsBaseClass.js  |   6 +-
 tests/baselines/reference/importHelpers.js    |   6 +-
 .../reference/importHelpersNoHelpers.js       |   6 +-
 .../reference/importHelpersNoModule.js        |   6 +-
 .../reference/importShadowsGlobalName.js      |   6 +-
 .../reference/importUsedInExtendsList1.js     |   6 +-
 .../reference/indexerConstraints2.js          |   6 +-
 .../reference/indirectSelfReference.js        |   6 +-
 .../reference/indirectSelfReferenceGeneric.js |   6 +-
 .../infinitelyExpandingTypesNonGenericBase.js |   6 +-
 .../inheritFromGenericTypeParameter.js        |   6 +-
 ...SameNamePrivatePropertiesFromSameOrigin.js |   6 +-
 tests/baselines/reference/inheritance.js      |   6 +-
 tests/baselines/reference/inheritance1.js     |   6 +-
 ...itanceGrandParentPrivateMemberCollision.js |   6 +-
 ...tPrivateMemberCollisionWithPublicMember.js |   6 +-
 ...tPublicMemberCollisionWithPrivateMember.js |   6 +-
 ...ritanceMemberAccessorOverridingAccessor.js |   6 +-
 ...heritanceMemberAccessorOverridingMethod.js |   6 +-
 ...ritanceMemberAccessorOverridingProperty.js |   6 +-
 ...inheritanceMemberFuncOverridingAccessor.js |   6 +-
 .../inheritanceMemberFuncOverridingMethod.js  |   6 +-
 ...inheritanceMemberFuncOverridingProperty.js |   6 +-
 ...ritanceMemberPropertyOverridingAccessor.js |   6 +-
 ...heritanceMemberPropertyOverridingMethod.js |   6 +-
 ...ritanceMemberPropertyOverridingProperty.js |   6 +-
 .../inheritanceOfGenericConstructorMethod1.js |   6 +-
 .../inheritanceOfGenericConstructorMethod2.js |   6 +-
 ...ritanceStaticAccessorOverridingAccessor.js |   6 +-
 ...heritanceStaticAccessorOverridingMethod.js |   6 +-
 ...ritanceStaticAccessorOverridingProperty.js |   6 +-
 ...inheritanceStaticFuncOverridingAccessor.js |   6 +-
 ...eStaticFuncOverridingAccessorOfFuncType.js |   6 +-
 .../inheritanceStaticFuncOverridingMethod.js  |   6 +-
 ...inheritanceStaticFuncOverridingProperty.js |   6 +-
 ...eStaticFuncOverridingPropertyOfFuncType.js |   6 +-
 ...taticFunctionOverridingInstanceProperty.js |   6 +-
 .../inheritanceStaticMembersCompatible.js     |   6 +-
 .../inheritanceStaticMembersIncompatible.js   |   6 +-
 ...ritanceStaticPropertyOverridingAccessor.js |   6 +-
 ...heritanceStaticPropertyOverridingMethod.js |   6 +-
 ...ritanceStaticPropertyOverridingProperty.js |   6 +-
 .../inheritedConstructorWithRestParams.js     |   6 +-
 .../inheritedConstructorWithRestParams2.js    |   6 +-
 .../inheritedModuleMembersForClodule.js       |   6 +-
 .../reference/instanceOfAssignability.js      |   6 +-
 ...nstancePropertiesInheritedIntoClassType.js |   6 +-
 .../reference/instanceSubtypeCheck2.js        |   6 +-
 ...nstanceofWithStructurallyIdenticalTypes.js |   6 +-
 .../instantiatedReturnTypeContravariance.js   |   6 +-
 .../reference/interfaceClassMerging.js        |   6 +-
 .../reference/interfaceClassMerging2.js       |   6 +-
 .../reference/interfaceExtendsClass1.js       |   6 +-
 .../interfaceExtendsClassWithPrivate1.js      |   6 +-
 .../interfaceExtendsClassWithPrivate2.js      |   6 +-
 .../reference/interfaceImplementation8.js     |   6 +-
 .../invalidModuleWithStatementsOfEveryKind.js |   6 +-
 .../invalidMultipleVariableDeclarations.js    |   6 +-
 .../reference/invalidReturnStatements.js      |   6 +-
 .../isolatedModulesImportExportElision.js     |   6 +-
 tests/baselines/reference/jsxViaImport.js     |   6 +-
 .../reference/keyofAndIndexedAccess.js        |   6 +-
 tests/baselines/reference/lambdaArgCrash.js   |   6 +-
 tests/baselines/reference/lift.js             |   6 +-
 tests/baselines/reference/localTypes1.js      |   6 +-
 tests/baselines/reference/m7Bugs.js           |   6 +-
 .../reference/mergedDeclarations5.js          |   6 +-
 .../reference/mergedDeclarations6.js          |   6 +-
 .../mergedInheritedClassInterface.js          |   6 +-
 .../mergedInterfacesWithInheritedPrivates2.js |   6 +-
 .../mergedInterfacesWithInheritedPrivates3.js |   6 +-
 .../missingPropertiesOfClassExpression.js     |   6 +-
 tests/baselines/reference/moduleAsBaseType.js |   6 +-
 .../moduleImportedForTypeArgumentPosition.js  |   6 +-
 .../moduleWithStatementsOfEveryKind.js        |   6 +-
 .../reference/multipleInheritance.js          |   6 +-
 .../mutuallyRecursiveGenericBaseTypes2.js     |   6 +-
 .../noImplicitAnyMissingGetAccessor.js        |   6 +-
 .../noImplicitAnyMissingSetAccessor.js        |   6 +-
 ...enericClassExtendingGenericClassWithAny.js |   6 +-
 ...cIndexerConstrainsPropertyDeclarations2.js |   6 +-
 .../reference/numericIndexerConstraint3.js    |   6 +-
 .../reference/numericIndexerConstraint4.js    |   6 +-
 .../reference/numericIndexerTyping2.js        |   6 +-
 ...objectCreationOfElementAccessExpression.js |   6 +-
 ...objectTypeHidingMembersOfExtendedObject.js |   6 +-
 ...objectTypesIdentityWithNumericIndexers1.js |   6 +-
 ...objectTypesIdentityWithNumericIndexers2.js |   6 +-
 ...objectTypesIdentityWithNumericIndexers3.js |   6 +-
 .../objectTypesIdentityWithPrivates.js        |   6 +-
 .../objectTypesIdentityWithPrivates2.js       |   6 +-
 .../objectTypesIdentityWithPrivates3.js       |   6 +-
 .../objectTypesIdentityWithStringIndexers.js  |   6 +-
 .../objectTypesIdentityWithStringIndexers2.js |   6 +-
 .../optionalConstructorArgInSuper.js          |   6 +-
 tests/baselines/reference/optionalMethods.js  |   6 +-
 .../reference/optionalParamArgsTest.js        |   6 +-
 .../reference/optionalParamInOverride.js      |   6 +-
 .../reference/optionalParameterProperty.js    |   6 +-
 .../baselines/reference/outModuleConcatAmd.js |   6 +-
 .../reference/outModuleConcatAmd.js.map       |   2 +-
 .../outModuleConcatAmd.sourcemap.txt          |  62 +-
 .../reference/outModuleConcatSystem.js        |   6 +-
 .../reference/outModuleConcatSystem.js.map    |   2 +-
 .../outModuleConcatSystem.sourcemap.txt       |  62 +-
 .../reference/outModuleTripleSlashRefs.js     |   6 +-
 .../reference/outModuleTripleSlashRefs.js.map |   2 +-
 .../outModuleTripleSlashRefs.sourcemap.txt    |  90 +-
 tests/baselines/reference/overload1.js        |   6 +-
 .../overloadOnConstConstraintChecks1.js       |   6 +-
 .../overloadOnConstConstraintChecks2.js       |   6 +-
 .../overloadOnConstConstraintChecks3.js       |   6 +-
 .../overloadOnConstConstraintChecks4.js       |   6 +-
 .../overloadOnConstantsInvalidOverload1.js    |   6 +-
 .../baselines/reference/overloadResolution.js |   6 +-
 .../overloadResolutionClassConstructors.js    |   6 +-
 .../overloadResolutionConstructors.js         |   6 +-
 .../reference/overloadingOnConstants1.js      |   6 +-
 .../reference/overloadingOnConstants2.js      |   6 +-
 .../overridingPrivateStaticMembers.js         |   6 +-
 .../reference/parseErrorInHeritageClause1.js  |   6 +-
 tests/baselines/reference/parser509630.js     |   6 +-
 tests/baselines/reference/parserAstSpans1.js  |   6 +-
 .../reference/parserClassDeclaration1.js      |   6 +-
 .../reference/parserClassDeclaration3.js      |   6 +-
 .../reference/parserClassDeclaration4.js      |   6 +-
 .../reference/parserClassDeclaration5.js      |   6 +-
 .../reference/parserClassDeclaration6.js      |   6 +-
 ...rrorRecovery_ExtendsOrImplementsClause2.js |   6 +-
 ...rrorRecovery_ExtendsOrImplementsClause4.js |   6 +-
 ...rrorRecovery_ExtendsOrImplementsClause5.js |   6 +-
 .../parserGenericsInTypeContexts1.js          |   6 +-
 .../parserGenericsInTypeContexts2.js          |   6 +-
 .../baselines/reference/parserRealSource10.js |   6 +-
 .../baselines/reference/parserRealSource11.js |   6 +-
 tests/baselines/reference/parserharness.js    |   6 +-
 ...artiallyAnnotatedFunctionInferenceError.js |   6 +-
 ...tatedFunctionInferenceWithTypeParameter.js |   6 +-
 tests/baselines/reference/primitiveMembers.js |   6 +-
 tests/baselines/reference/privacyClass.js     |   6 +-
 .../privacyClassExtendsClauseDeclFile.js      |  12 +-
 tests/baselines/reference/privacyGloClass.js  |   6 +-
 .../reference/privateAccessInSubclass1.js     |   6 +-
 .../privateInstanceMemberAccessibility.js     |   6 +-
 ...tedMembersAreNotAccessibleDestructuring.js |   6 +-
 .../privateStaticMemberAccessibility.js       |   6 +-
 .../privateStaticNotAccessibleInClodule2.js   |   6 +-
 .../amd/testGlo.js                            |   6 +-
 .../node/testGlo.js                           |   6 +-
 .../reference/project/prologueEmit/amd/out.js |   6 +-
 .../project/prologueEmit/node/out.js          |   6 +-
 .../amd/m'ain.js                              |   6 +-
 .../node/m'ain.js                             |   6 +-
 .../reference/propertiesAndIndexers.js        |   6 +-
 tests/baselines/reference/propertyAccess.js   |   6 +-
 ...tyAccessOnTypeParameterWithConstraints2.js |   6 +-
 ...tyAccessOnTypeParameterWithConstraints3.js |   6 +-
 ...tyAccessOnTypeParameterWithConstraints5.js |   6 +-
 ...sPropertyAccessibleWithinNestedSubclass.js |   6 +-
 ...PropertyAccessibleWithinNestedSubclass1.js |   6 +-
 ...edClassPropertyAccessibleWithinSubclass.js |   6 +-
 ...dClassPropertyAccessibleWithinSubclass2.js |   6 +-
 ...dClassPropertyAccessibleWithinSubclass3.js |   6 +-
 .../protectedInstanceMemberAccessibility.js   |   6 +-
 tests/baselines/reference/protectedMembers.js |   6 +-
 ...icClassPropertyAccessibleWithinSubclass.js |   6 +-
 ...cClassPropertyAccessibleWithinSubclass2.js |   6 +-
 ...solution-does-not-affect-class-heritage.js |   6 +-
 .../readonlyConstructorAssignment.js          |   6 +-
 .../reference/recursiveBaseCheck3.js          |   6 +-
 .../reference/recursiveBaseCheck4.js          |   6 +-
 .../reference/recursiveBaseCheck6.js          |   6 +-
 .../recursiveBaseConstructorCreation1.js      |   6 +-
 ...ssInstantiationsWithDefaultConstructors.js |   6 +-
 .../reference/recursiveClassReferenceTest.js  |   6 +-
 .../recursiveClassReferenceTest.js.map        |   2 +-
 .../recursiveClassReferenceTest.sourcemap.txt | 776 +++++++++---------
 .../reference/recursiveComplicatedClasses.js  |   6 +-
 ...sivelySpecializedConstructorDeclaration.js |   6 +-
 .../reference/reexportClassDefinition.js      |   6 +-
 ...lassDeclarationWhenInBaseTypeResolution.js |   6 +-
 .../reference/returnInConstructor1.js         |   6 +-
 tests/baselines/reference/returnStatements.js |   6 +-
 ...peCheckExtendedClassInsidePublicMethod2.js |   6 +-
 ...peCheckExtendedClassInsideStaticMethod1.js |   6 +-
 tests/baselines/reference/scopeTests.js       |   6 +-
 .../reference/shadowPrivateMembers.js         |   6 +-
 ...sWithDefaultConstructorAndExtendsClause.js |   6 +-
 ...hDefaultConstructorAndExtendsClause.js.map |   2 +-
 ...tConstructorAndExtendsClause.sourcemap.txt |  78 +-
 .../specializedInheritedConstructors1.js      |   6 +-
 .../specializedOverloadWithRestParameters.js  |   6 +-
 tests/baselines/reference/staticFactory1.js   |   6 +-
 .../baselines/reference/staticInheritance.js  |   6 +-
 .../staticMemberAccessOffDerivedType1.js      |   6 +-
 tests/baselines/reference/staticPropSuper.js  |   6 +-
 .../reference/strictModeInConstructor.js      |   6 +-
 .../reference/strictModeReservedWord.js       |   6 +-
 ...trictModeReservedWordInClassDeclaration.js |   6 +-
 ...gIndexerConstrainsPropertyDeclarations2.js |   6 +-
 .../reference/subtypesOfTypeParameter.js      |   6 +-
 .../subtypesOfTypeParameterWithConstraints.js |   6 +-
 ...subtypesOfTypeParameterWithConstraints4.js |   6 +-
 ...OfTypeParameterWithRecursiveConstraints.js |   6 +-
 .../reference/subtypingTransitivity.js        |   6 +-
 .../reference/subtypingWithCallSignatures2.js |   6 +-
 .../reference/subtypingWithCallSignatures3.js |   6 +-
 .../reference/subtypingWithCallSignatures4.js |   6 +-
 .../subtypingWithConstructSignatures2.js      |   6 +-
 .../subtypingWithConstructSignatures3.js      |   6 +-
 .../subtypingWithConstructSignatures4.js      |   6 +-
 .../subtypingWithConstructSignatures5.js      |   6 +-
 .../subtypingWithConstructSignatures6.js      |   6 +-
 .../reference/subtypingWithNumericIndexer.js  |   6 +-
 .../reference/subtypingWithNumericIndexer3.js |   6 +-
 .../reference/subtypingWithNumericIndexer4.js |   6 +-
 .../reference/subtypingWithObjectMembers.js   |   6 +-
 .../reference/subtypingWithObjectMembers4.js  |   6 +-
 ...subtypingWithObjectMembersAccessibility.js |   6 +-
 ...ubtypingWithObjectMembersAccessibility2.js |   6 +-
 .../reference/subtypingWithStringIndexer.js   |   6 +-
 .../reference/subtypingWithStringIndexer3.js  |   6 +-
 .../reference/subtypingWithStringIndexer4.js  |   6 +-
 tests/baselines/reference/super.js            |   6 +-
 tests/baselines/reference/super1.js           |   6 +-
 tests/baselines/reference/super2.js           |   6 +-
 tests/baselines/reference/superAccess.js      |   6 +-
 tests/baselines/reference/superAccess2.js     |   6 +-
 .../reference/superAccessInFatArrow1.js       |   6 +-
 .../reference/superCallArgsMustMatch.js       |   6 +-
 .../reference/superCallAssignResult.js        |   6 +-
 .../superCallBeforeThisAccessing1.js          |   6 +-
 .../superCallBeforeThisAccessing2.js          |   6 +-
 .../superCallBeforeThisAccessing3.js          |   6 +-
 .../superCallBeforeThisAccessing4.js          |   6 +-
 .../superCallBeforeThisAccessing5.js          |   6 +-
 .../superCallBeforeThisAccessing6.js          |   6 +-
 .../superCallBeforeThisAccessing7.js          |   6 +-
 .../superCallBeforeThisAccessing8.js          |   6 +-
 ...allFromClassThatDerivesFromGenericType1.js |   6 +-
 ...allFromClassThatDerivesFromGenericType2.js |   6 +-
 ...eButWithIncorrectNumberOfTypeArguments1.js |   6 +-
 ...sFromGenericTypeButWithNoTypeArguments1.js |   6 +-
 ...ivesNonGenericTypeButWithTypeArguments1.js |   6 +-
 .../reference/superCallInNonStaticMethod.js   |   6 +-
 .../reference/superCallInStaticMethod.js      |   6 +-
 .../superCallInsideClassDeclaration.js        |   6 +-
 .../superCallInsideClassExpression.js         |   6 +-
 .../superCallInsideObjectLiteralExpression.js |   6 +-
 .../reference/superCallOutsideConstructor.js  |   6 +-
 .../superCallParameterContextualTyping1.js    |   6 +-
 .../superCallParameterContextualTyping2.js    |   6 +-
 .../superCallParameterContextualTyping3.js    |   6 +-
 .../reference/superCallWithCommentEmit01.js   |   6 +-
 .../superCallWithMissingBaseClass.js          |   6 +-
 tests/baselines/reference/superCalls.js       |   6 +-
 .../reference/superCallsInConstructor.js      |   6 +-
 tests/baselines/reference/superErrors.js      |   6 +-
 .../baselines/reference/superInCatchBlock1.js |   6 +-
 .../reference/superInConstructorParam1.js     |   6 +-
 tests/baselines/reference/superInLambdas.js   |   6 +-
 .../reference/superInObjectLiterals_ES5.js    |   6 +-
 tests/baselines/reference/superNewCall1.js    |   6 +-
 .../reference/superPropertyAccess.js          |   6 +-
 .../reference/superPropertyAccess1.js         |   6 +-
 .../reference/superPropertyAccess2.js         |   6 +-
 ...essInComputedPropertiesOfNestedType_ES5.js |   6 +-
 .../reference/superPropertyAccessNoError.js   |   6 +-
 .../reference/superPropertyAccess_ES5.js      |   6 +-
 .../reference/superSymbolIndexedAccess5.js    |   6 +-
 .../reference/superSymbolIndexedAccess6.js    |   6 +-
 .../superWithGenericSpecialization.js         |   6 +-
 .../baselines/reference/superWithGenerics.js  |   6 +-
 .../reference/superWithTypeArgument.js        |   6 +-
 .../reference/superWithTypeArgument2.js       |   6 +-
 .../reference/superWithTypeArgument3.js       |   6 +-
 ...side-object-literal-getters-and-setters.js |   6 +-
 tests/baselines/reference/switchStatements.js |   6 +-
 .../reference/systemModuleWithSuperClass.js   |   6 +-
 .../reference/targetTypeBaseCalls.js          |   6 +-
 .../reference/thisInInvalidContexts.js        |   6 +-
 .../thisInInvalidContextsExternalModule.js    |   6 +-
 tests/baselines/reference/thisInSuperCall.js  |   6 +-
 tests/baselines/reference/thisInSuperCall1.js |   6 +-
 tests/baselines/reference/thisInSuperCall2.js |   6 +-
 tests/baselines/reference/thisInSuperCall3.js |   6 +-
 .../reference/thisTypeInFunctions.js          |   6 +-
 .../reference/thisTypeInFunctionsNegative.js  |   6 +-
 .../tsxCorrectlyParseLessThanComparison1.js   |   6 +-
 .../baselines/reference/tsxDynamicTagName5.js |   6 +-
 .../baselines/reference/tsxDynamicTagName7.js |   6 +-
 .../baselines/reference/tsxDynamicTagName8.js |   6 +-
 .../baselines/reference/tsxDynamicTagName9.js |   6 +-
 .../reference/tsxExternalModuleEmit1.js       |  12 +-
 .../tsxStatelessFunctionComponents2.js        |   6 +-
 .../reference/tsxUnionTypeComponent1.js       |   6 +-
 tests/baselines/reference/typeAssertions.js   |   6 +-
 .../baselines/reference/typeGuardFunction.js  |   6 +-
 .../reference/typeGuardFunctionErrors.js      |   6 +-
 .../reference/typeGuardFunctionGenerics.js    |   6 +-
 .../reference/typeGuardFunctionOfFormThis.js  |   6 +-
 .../typeGuardFunctionOfFormThisErrors.js      |   6 +-
 .../reference/typeGuardOfFormInstanceOf.js    |   6 +-
 .../reference/typeGuardOfFormIsType.js        |   6 +-
 .../reference/typeGuardOfFormThisMember.js    |   6 +-
 .../typeGuardOfFormThisMemberErrors.js        |   6 +-
 tests/baselines/reference/typeMatch2.js       |   6 +-
 tests/baselines/reference/typeOfSuperCall.js  |   6 +-
 .../reference/typeParameterAsBaseClass.js     |   6 +-
 .../reference/typeParameterAsBaseType.js      |   6 +-
 .../reference/typeParameterExtendingUnion1.js |   6 +-
 .../reference/typeParameterExtendingUnion2.js |   6 +-
 .../baselines/reference/typeRelationships.js  |   6 +-
 .../baselines/reference/typeValueConflict1.js |   6 +-
 .../baselines/reference/typeValueConflict2.js |   6 +-
 tests/baselines/reference/typeofClass2.js     |   6 +-
 .../typesWithSpecializedCallSignatures.js     |   6 +-
 ...typesWithSpecializedConstructSignatures.js |   6 +-
 tests/baselines/reference/undeclaredBase.js   |   6 +-
 .../undefinedIsSubtypeOfEverything.js         |   6 +-
 .../baselines/reference/underscoreMapFirst.js |   6 +-
 .../underscoreThisInDerivedClass01.js         |   6 +-
 .../underscoreThisInDerivedClass02.js         |   6 +-
 .../reference/unionTypeEquivalence.js         |   6 +-
 .../reference/unionTypeFromArrayLiteral.js    |   6 +-
 .../reference/unionTypesAssignability.js      |   6 +-
 tests/baselines/reference/unknownSymbols1.js  |   6 +-
 .../reference/unspecializedConstraints.js     |   6 +-
 ...untypedFunctionCallsWithTypeParameters1.js |   6 +-
 .../reference/unusedClassesinNamespace4.js    |   6 +-
 .../unusedIdentifiersConsolidated1.js         |   6 +-
 .../reference/validUseOfThisInSuper.js        |   6 +-
 .../reference/varArgsOnConstructorTypes.js    |   6 +-
 666 files changed, 4006 insertions(+), 1326 deletions(-)

diff --git a/src/compiler/transformers/es2015.ts b/src/compiler/transformers/es2015.ts
index 5dc78701316..fff52a8705e 100644
--- a/src/compiler/transformers/es2015.ts
+++ b/src/compiler/transformers/es2015.ts
@@ -3338,7 +3338,11 @@ namespace ts {
         priority: 0,
         text: `
             var __extends = (this && this.__extends) || function (d, b) {
-                Object.setPrototypeOf(d, b);
+                if (typeof Object.setPrototypeOf === "function") {
+                    Object.setPrototypeOf(d, b);
+                } else {
+                    d.__proto__ = b;
+                }
                 function __() { this.constructor = d; }
                 d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
             };`
diff --git a/tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js b/tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js
index b15cd7f6eb7..fb158c687ba 100644
--- a/tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js
+++ b/tests/baselines/reference/ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js
@@ -22,7 +22,11 @@ module A {
 
 //// [ExportClassWithAccessibleTypesInTypeParameterConstraintsClassHeritageListMemberTypeAnnotations.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.js b/tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.js
index 955adc72817..ec67e66bd3f 100644
--- a/tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.js
+++ b/tests/baselines/reference/ExportClassWithInaccessibleTypeInTypeParameterConstraint.js
@@ -26,7 +26,11 @@ module A {
 
 //// [ExportClassWithInaccessibleTypeInTypeParameterConstraint.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/abstractClassInLocalScope.js b/tests/baselines/reference/abstractClassInLocalScope.js
index b413326e26a..8e16f9ccc29 100644
--- a/tests/baselines/reference/abstractClassInLocalScope.js
+++ b/tests/baselines/reference/abstractClassInLocalScope.js
@@ -9,7 +9,11 @@
 
 //// [abstractClassInLocalScope.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/abstractClassInLocalScopeIsAbstract.js b/tests/baselines/reference/abstractClassInLocalScopeIsAbstract.js
index f143171b54c..40eae697b44 100644
--- a/tests/baselines/reference/abstractClassInLocalScopeIsAbstract.js
+++ b/tests/baselines/reference/abstractClassInLocalScopeIsAbstract.js
@@ -9,7 +9,11 @@
 
 //// [abstractClassInLocalScopeIsAbstract.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/abstractProperty.js b/tests/baselines/reference/abstractProperty.js
index 12735de42cb..900f7aebcdd 100644
--- a/tests/baselines/reference/abstractProperty.js
+++ b/tests/baselines/reference/abstractProperty.js
@@ -23,7 +23,11 @@ class C extends B {
 
 //// [abstractProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/abstractPropertyNegative.js b/tests/baselines/reference/abstractPropertyNegative.js
index eaad20d1804..fa137057be4 100644
--- a/tests/baselines/reference/abstractPropertyNegative.js
+++ b/tests/baselines/reference/abstractPropertyNegative.js
@@ -45,7 +45,11 @@ abstract class AbstractAccessorMismatch {
 
 //// [abstractPropertyNegative.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/accessOverriddenBaseClassMember1.js b/tests/baselines/reference/accessOverriddenBaseClassMember1.js
index 2d06be8df96..b468f1307df 100644
--- a/tests/baselines/reference/accessOverriddenBaseClassMember1.js
+++ b/tests/baselines/reference/accessOverriddenBaseClassMember1.js
@@ -17,7 +17,11 @@ class ColoredPoint extends Point {
 
 //// [accessOverriddenBaseClassMember1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/accessors_spec_section-4.5_inference.js b/tests/baselines/reference/accessors_spec_section-4.5_inference.js
index eddb75c2666..aacadd6589f 100644
--- a/tests/baselines/reference/accessors_spec_section-4.5_inference.js
+++ b/tests/baselines/reference/accessors_spec_section-4.5_inference.js
@@ -26,7 +26,11 @@ class LanguageSpec_section_4_5_inference {
 
 //// [accessors_spec_section-4.5_inference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInAccessorsOfClass.js b/tests/baselines/reference/aliasUsageInAccessorsOfClass.js
index 817e589d995..df8662ac8cf 100644
--- a/tests/baselines/reference/aliasUsageInAccessorsOfClass.js
+++ b/tests/baselines/reference/aliasUsageInAccessorsOfClass.js
@@ -38,7 +38,11 @@ exports.Model = Model;
 //// [aliasUsage1_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInArray.js b/tests/baselines/reference/aliasUsageInArray.js
index e0d30fb608b..a8606050394 100644
--- a/tests/baselines/reference/aliasUsageInArray.js
+++ b/tests/baselines/reference/aliasUsageInArray.js
@@ -32,7 +32,11 @@ exports.Model = Model;
 //// [aliasUsageInArray_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInFunctionExpression.js b/tests/baselines/reference/aliasUsageInFunctionExpression.js
index 35bf66fed02..2ce51261eaa 100644
--- a/tests/baselines/reference/aliasUsageInFunctionExpression.js
+++ b/tests/baselines/reference/aliasUsageInFunctionExpression.js
@@ -31,7 +31,11 @@ exports.Model = Model;
 //// [aliasUsageInFunctionExpression_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInGenericFunction.js b/tests/baselines/reference/aliasUsageInGenericFunction.js
index 373aa0c3b40..8e69665b03c 100644
--- a/tests/baselines/reference/aliasUsageInGenericFunction.js
+++ b/tests/baselines/reference/aliasUsageInGenericFunction.js
@@ -35,7 +35,11 @@ exports.Model = Model;
 //// [aliasUsageInGenericFunction_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInIndexerOfClass.js b/tests/baselines/reference/aliasUsageInIndexerOfClass.js
index 9769a4b005f..cf96549def6 100644
--- a/tests/baselines/reference/aliasUsageInIndexerOfClass.js
+++ b/tests/baselines/reference/aliasUsageInIndexerOfClass.js
@@ -37,7 +37,11 @@ exports.Model = Model;
 //// [aliasUsageInIndexerOfClass_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInObjectLiteral.js b/tests/baselines/reference/aliasUsageInObjectLiteral.js
index 2f4abf75161..d660bf2db67 100644
--- a/tests/baselines/reference/aliasUsageInObjectLiteral.js
+++ b/tests/baselines/reference/aliasUsageInObjectLiteral.js
@@ -32,7 +32,11 @@ exports.Model = Model;
 //// [aliasUsageInObjectLiteral_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInOrExpression.js b/tests/baselines/reference/aliasUsageInOrExpression.js
index c4902a1b894..e81917ed8a3 100644
--- a/tests/baselines/reference/aliasUsageInOrExpression.js
+++ b/tests/baselines/reference/aliasUsageInOrExpression.js
@@ -35,7 +35,11 @@ exports.Model = Model;
 //// [aliasUsageInOrExpression_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInTypeArgumentOfExtendsClause.js b/tests/baselines/reference/aliasUsageInTypeArgumentOfExtendsClause.js
index c79f820b106..ee4a62008b1 100644
--- a/tests/baselines/reference/aliasUsageInTypeArgumentOfExtendsClause.js
+++ b/tests/baselines/reference/aliasUsageInTypeArgumentOfExtendsClause.js
@@ -35,7 +35,11 @@ exports.Model = Model;
 //// [aliasUsageInTypeArgumentOfExtendsClause_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -51,7 +55,11 @@ exports.VisualizationModel = VisualizationModel;
 //// [aliasUsageInTypeArgumentOfExtendsClause_main.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/aliasUsageInVarAssignment.js b/tests/baselines/reference/aliasUsageInVarAssignment.js
index 87c41811d4a..83c9bf080be 100644
--- a/tests/baselines/reference/aliasUsageInVarAssignment.js
+++ b/tests/baselines/reference/aliasUsageInVarAssignment.js
@@ -31,7 +31,11 @@ exports.Model = Model;
 //// [aliasUsageInVarAssignment_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/ambiguousOverloadResolution.js b/tests/baselines/reference/ambiguousOverloadResolution.js
index 9b141141862..319d3a75d01 100644
--- a/tests/baselines/reference/ambiguousOverloadResolution.js
+++ b/tests/baselines/reference/ambiguousOverloadResolution.js
@@ -10,7 +10,11 @@ var t: number = f(x, x); // Not an error
 
 //// [ambiguousOverloadResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/apparentTypeSubtyping.js b/tests/baselines/reference/apparentTypeSubtyping.js
index dc30b51a448..8cc81a46cd7 100644
--- a/tests/baselines/reference/apparentTypeSubtyping.js
+++ b/tests/baselines/reference/apparentTypeSubtyping.js
@@ -25,7 +25,11 @@ class Derived2<U extends String> extends Base2 { // error because of the prototy
 // subtype checks use the apparent type of the target type
 // S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S:
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/apparentTypeSupertype.js b/tests/baselines/reference/apparentTypeSupertype.js
index bb002a9798d..ba5d63e3579 100644
--- a/tests/baselines/reference/apparentTypeSupertype.js
+++ b/tests/baselines/reference/apparentTypeSupertype.js
@@ -15,7 +15,11 @@ class Derived<U extends String> extends Base { // error
 // subtype checks use the apparent type of the target type
 // S is a subtype of a type T, and T is a supertype of S, if one of the following is true, where S' denotes the apparent type (section 3.8.1) of S:
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayAssignmentTest1.js b/tests/baselines/reference/arrayAssignmentTest1.js
index 410fb80b323..ac8ada2d86f 100644
--- a/tests/baselines/reference/arrayAssignmentTest1.js
+++ b/tests/baselines/reference/arrayAssignmentTest1.js
@@ -87,7 +87,11 @@ arr_any = i1; // should be an error - is
 
 //// [arrayAssignmentTest1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayAssignmentTest2.js b/tests/baselines/reference/arrayAssignmentTest2.js
index e051b8187cf..a112a5a7a90 100644
--- a/tests/baselines/reference/arrayAssignmentTest2.js
+++ b/tests/baselines/reference/arrayAssignmentTest2.js
@@ -61,7 +61,11 @@ arr_any = i1; // should be an error - is
 
 //// [arrayAssignmentTest2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayBestCommonTypes.js b/tests/baselines/reference/arrayBestCommonTypes.js
index acaa6c76ffc..9ce41a2563a 100644
--- a/tests/baselines/reference/arrayBestCommonTypes.js
+++ b/tests/baselines/reference/arrayBestCommonTypes.js
@@ -109,7 +109,11 @@ module NonEmptyTypes {
 
 //// [arrayBestCommonTypes.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayLiteralTypeInference.js b/tests/baselines/reference/arrayLiteralTypeInference.js
index d836e0afe1d..a14277c795b 100644
--- a/tests/baselines/reference/arrayLiteralTypeInference.js
+++ b/tests/baselines/reference/arrayLiteralTypeInference.js
@@ -53,7 +53,11 @@ var z3: { id: number }[] =
 
 //// [arrayLiteralTypeInference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayLiterals.js b/tests/baselines/reference/arrayLiterals.js
index 5e57d827c72..1e5dcd2e45e 100644
--- a/tests/baselines/reference/arrayLiterals.js
+++ b/tests/baselines/reference/arrayLiterals.js
@@ -39,7 +39,11 @@ var context4: Base[] = [new Derived1(), new Derived1()];
 //// [arrayLiterals.js]
 // Empty array literal with no contextual type has type Undefined[]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayLiteralsWithRecursiveGenerics.js b/tests/baselines/reference/arrayLiteralsWithRecursiveGenerics.js
index 5b8237c2556..e6e097c8b44 100644
--- a/tests/baselines/reference/arrayLiteralsWithRecursiveGenerics.js
+++ b/tests/baselines/reference/arrayLiteralsWithRecursiveGenerics.js
@@ -27,7 +27,11 @@ var as = [list, myDerivedList]; // List<number>[]
 
 //// [arrayLiteralsWithRecursiveGenerics.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.js b/tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.js
index 6fecfadd07b..701811e33de 100644
--- a/tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.js
+++ b/tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.js
@@ -21,7 +21,11 @@ rrb = cra; // error: 'A' is not assignable to 'B'
 
 //// [arrayOfSubtypeIsAssignableToReadonlyArray.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/arrowFunctionContexts.js b/tests/baselines/reference/arrowFunctionContexts.js
index 7075cdc0a58..e425ebf9337 100644
--- a/tests/baselines/reference/arrowFunctionContexts.js
+++ b/tests/baselines/reference/arrowFunctionContexts.js
@@ -98,7 +98,11 @@ var asserted2: any;
 
 //// [arrowFunctionContexts.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures3.js b/tests/baselines/reference/assignmentCompatWithCallSignatures3.js
index d4761781bd3..f241b28597d 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignatures3.js
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures3.js
@@ -102,7 +102,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithCallSignatures3.js]
 // these are all permitted with the current rules, since we do not do contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures4.js b/tests/baselines/reference/assignmentCompatWithCallSignatures4.js
index 1a3d939ba23..eade43f4dc8 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignatures4.js
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures4.js
@@ -101,7 +101,11 @@ module Errors {
 //// [assignmentCompatWithCallSignatures4.js]
 // These are mostly permitted with the current loose rules. All ok unless otherwise noted.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures5.js b/tests/baselines/reference/assignmentCompatWithCallSignatures5.js
index 8d33f3565bf..36a024cbd3f 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignatures5.js
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures5.js
@@ -68,7 +68,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithCallSignatures5.js]
 // checking assignment compat for function types. No errors in this file
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithCallSignatures6.js b/tests/baselines/reference/assignmentCompatWithCallSignatures6.js
index 5949ad582fa..eb727863c77 100644
--- a/tests/baselines/reference/assignmentCompatWithCallSignatures6.js
+++ b/tests/baselines/reference/assignmentCompatWithCallSignatures6.js
@@ -45,7 +45,11 @@ b16 = x.a16;
 //// [assignmentCompatWithCallSignatures6.js]
 // checking assignment compatibility relations for function types. All valid
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures3.js b/tests/baselines/reference/assignmentCompatWithConstructSignatures3.js
index 97da2c58848..bff2b84f273 100644
--- a/tests/baselines/reference/assignmentCompatWithConstructSignatures3.js
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures3.js
@@ -102,7 +102,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithConstructSignatures3.js]
 // checking assignment compatibility relations for function types. All of these are valid.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures4.js b/tests/baselines/reference/assignmentCompatWithConstructSignatures4.js
index 44e9c8e8a36..8aefc846d9b 100644
--- a/tests/baselines/reference/assignmentCompatWithConstructSignatures4.js
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures4.js
@@ -101,7 +101,11 @@ module Errors {
 //// [assignmentCompatWithConstructSignatures4.js]
 // checking assignment compatibility relations for function types.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures5.js b/tests/baselines/reference/assignmentCompatWithConstructSignatures5.js
index a80ece9d4d5..b21074b8ff3 100644
--- a/tests/baselines/reference/assignmentCompatWithConstructSignatures5.js
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures5.js
@@ -68,7 +68,11 @@ b18 = a18; // ok
 //// [assignmentCompatWithConstructSignatures5.js]
 // checking assignment compat for function types. All valid
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithConstructSignatures6.js b/tests/baselines/reference/assignmentCompatWithConstructSignatures6.js
index ea5c5c61e3b..95f585e8929 100644
--- a/tests/baselines/reference/assignmentCompatWithConstructSignatures6.js
+++ b/tests/baselines/reference/assignmentCompatWithConstructSignatures6.js
@@ -45,7 +45,11 @@ b16 = x.a16;
 //// [assignmentCompatWithConstructSignatures6.js]
 // checking assignment compatibility relations for function types. All valid.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithNumericIndexer.js b/tests/baselines/reference/assignmentCompatWithNumericIndexer.js
index f5ec41091e0..05dce80507d 100644
--- a/tests/baselines/reference/assignmentCompatWithNumericIndexer.js
+++ b/tests/baselines/reference/assignmentCompatWithNumericIndexer.js
@@ -46,7 +46,11 @@ module Generics {
 //// [assignmentCompatWithNumericIndexer.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithNumericIndexer3.js b/tests/baselines/reference/assignmentCompatWithNumericIndexer3.js
index c6e262c4446..7785aa2b01f 100644
--- a/tests/baselines/reference/assignmentCompatWithNumericIndexer3.js
+++ b/tests/baselines/reference/assignmentCompatWithNumericIndexer3.js
@@ -43,7 +43,11 @@ module Generics {
 //// [assignmentCompatWithNumericIndexer3.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithObjectMembers4.js b/tests/baselines/reference/assignmentCompatWithObjectMembers4.js
index b7ff16e11fc..dbc0612153f 100644
--- a/tests/baselines/reference/assignmentCompatWithObjectMembers4.js
+++ b/tests/baselines/reference/assignmentCompatWithObjectMembers4.js
@@ -94,7 +94,11 @@ module WithBase {
 //// [assignmentCompatWithObjectMembers4.js]
 // members N and M of types S and T have the same name, same accessibility, same optionality, and N is not assignable M
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality.js b/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality.js
index b5148d063a7..fcbea350773 100644
--- a/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality.js
+++ b/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality.js
@@ -91,7 +91,11 @@ module SourceHasOptional {
 //// [assignmentCompatWithObjectMembersOptionality.js]
 // Derived member is not optional but base member is, should be ok
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality2.js b/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality2.js
index 4b22c469791..91f212c9fd9 100644
--- a/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality2.js
+++ b/tests/baselines/reference/assignmentCompatWithObjectMembersOptionality2.js
@@ -93,7 +93,11 @@ module SourceHasOptional {
 // M is optional and S contains no property with the same name as M
 // N is optional and T contains no property with the same name as N
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentCompatWithStringIndexer.js b/tests/baselines/reference/assignmentCompatWithStringIndexer.js
index b319af595cd..a0fb08df8d2 100644
--- a/tests/baselines/reference/assignmentCompatWithStringIndexer.js
+++ b/tests/baselines/reference/assignmentCompatWithStringIndexer.js
@@ -56,7 +56,11 @@ module Generics {
 //// [assignmentCompatWithStringIndexer.js]
 // index signatures must be compatible in assignments
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/assignmentLHSIsValue.js b/tests/baselines/reference/assignmentLHSIsValue.js
index add2c59e15f..e4fa0fcc6b7 100644
--- a/tests/baselines/reference/assignmentLHSIsValue.js
+++ b/tests/baselines/reference/assignmentLHSIsValue.js
@@ -72,7 +72,11 @@ foo() = value;
 
 //// [assignmentLHSIsValue.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/asyncImportedPromise_es5.js b/tests/baselines/reference/asyncImportedPromise_es5.js
index f13b4f962c7..a90d4254c61 100644
--- a/tests/baselines/reference/asyncImportedPromise_es5.js
+++ b/tests/baselines/reference/asyncImportedPromise_es5.js
@@ -12,7 +12,11 @@ class Test {
 //// [task.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/autolift4.js b/tests/baselines/reference/autolift4.js
index 5d27475ba42..d516e1e9b7b 100644
--- a/tests/baselines/reference/autolift4.js
+++ b/tests/baselines/reference/autolift4.js
@@ -25,7 +25,11 @@ class Point3D extends Point {
 
 //// [autolift4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/baseCheck.js b/tests/baselines/reference/baseCheck.js
index 80271d13e83..9684189d565 100644
--- a/tests/baselines/reference/baseCheck.js
+++ b/tests/baselines/reference/baseCheck.js
@@ -31,7 +31,11 @@ function f() {
 
 //// [baseCheck.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/baseIndexSignatureResolution.js b/tests/baselines/reference/baseIndexSignatureResolution.js
index bd6dd5a40e8..b1cb7c05ffc 100644
--- a/tests/baselines/reference/baseIndexSignatureResolution.js
+++ b/tests/baselines/reference/baseIndexSignatureResolution.js
@@ -26,7 +26,11 @@ var z: Derived = b.foo();
 
 //// [baseIndexSignatureResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/baseTypeOrderChecking.js b/tests/baselines/reference/baseTypeOrderChecking.js
index 1c87fb1dd5d..5f7f6550ab9 100644
--- a/tests/baselines/reference/baseTypeOrderChecking.js
+++ b/tests/baselines/reference/baseTypeOrderChecking.js
@@ -38,7 +38,11 @@ class Class4<T> extends Class3<T>
 
 //// [baseTypeOrderChecking.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/baseTypeWrappingInstantiationChain.js b/tests/baselines/reference/baseTypeWrappingInstantiationChain.js
index cc6c091b6c7..822c9584e1f 100644
--- a/tests/baselines/reference/baseTypeWrappingInstantiationChain.js
+++ b/tests/baselines/reference/baseTypeWrappingInstantiationChain.js
@@ -29,7 +29,11 @@ class C<T1> extends CBase<T1> {
 
 //// [baseTypeWrappingInstantiationChain.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/bases.js b/tests/baselines/reference/bases.js
index f23750c4391..e45b934f1ad 100644
--- a/tests/baselines/reference/bases.js
+++ b/tests/baselines/reference/bases.js
@@ -22,7 +22,11 @@ new C().y;
 
 //// [bases.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/bestCommonTypeOfConditionalExpressions.js b/tests/baselines/reference/bestCommonTypeOfConditionalExpressions.js
index 755c3f4ab84..c5e124e638a 100644
--- a/tests/baselines/reference/bestCommonTypeOfConditionalExpressions.js
+++ b/tests/baselines/reference/bestCommonTypeOfConditionalExpressions.js
@@ -30,7 +30,11 @@ function foo5<T, U>(t: T, u: U): Object {
 // conditional expressions return the best common type of the branches plus contextual type (using the first candidate if multiple BCTs exist)
 // no errors expected here
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.js b/tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.js
index 796706dd248..1390eeb5a5d 100644
--- a/tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.js
+++ b/tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.js
@@ -28,7 +28,11 @@ function foo3<T extends U, U extends V, V>(t: T, u: U) {
 // conditional expressions return the best common type of the branches plus contextual type (using the first candidate if multiple BCTs exist)
 // these are errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/bestCommonTypeOfTuple2.js b/tests/baselines/reference/bestCommonTypeOfTuple2.js
index 1bd3ac45bcc..17c9242e6aa 100644
--- a/tests/baselines/reference/bestCommonTypeOfTuple2.js
+++ b/tests/baselines/reference/bestCommonTypeOfTuple2.js
@@ -24,7 +24,11 @@ var e51 = t5[2]; // {}
 
 //// [bestCommonTypeOfTuple2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/callSignatureAssignabilityInInheritance2.js b/tests/baselines/reference/callSignatureAssignabilityInInheritance2.js
index 3c581096d6b..3d7d1167db5 100644
--- a/tests/baselines/reference/callSignatureAssignabilityInInheritance2.js
+++ b/tests/baselines/reference/callSignatureAssignabilityInInheritance2.js
@@ -72,7 +72,11 @@ interface I extends A {
 //// [callSignatureAssignabilityInInheritance2.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/callSignatureAssignabilityInInheritance3.js b/tests/baselines/reference/callSignatureAssignabilityInInheritance3.js
index 909a9bbb8cb..8674a9def64 100644
--- a/tests/baselines/reference/callSignatureAssignabilityInInheritance3.js
+++ b/tests/baselines/reference/callSignatureAssignabilityInInheritance3.js
@@ -117,7 +117,11 @@ module Errors {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // error cases
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/callSignatureAssignabilityInInheritance4.js b/tests/baselines/reference/callSignatureAssignabilityInInheritance4.js
index d42769a1e67..3173b6bd661 100644
--- a/tests/baselines/reference/callSignatureAssignabilityInInheritance4.js
+++ b/tests/baselines/reference/callSignatureAssignabilityInInheritance4.js
@@ -52,7 +52,11 @@ interface I extends A {
 //// [callSignatureAssignabilityInInheritance4.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/callSignatureAssignabilityInInheritance5.js b/tests/baselines/reference/callSignatureAssignabilityInInheritance5.js
index 94f5fecd2f8..b1c387fb3e7 100644
--- a/tests/baselines/reference/callSignatureAssignabilityInInheritance5.js
+++ b/tests/baselines/reference/callSignatureAssignabilityInInheritance5.js
@@ -52,7 +52,11 @@ interface I extends B {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // same as subtypingWithCallSignatures2 just with an extra level of indirection in the inheritance chain
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/callSignatureAssignabilityInInheritance6.js b/tests/baselines/reference/callSignatureAssignabilityInInheritance6.js
index b73ed7070d8..1b7688262cb 100644
--- a/tests/baselines/reference/callSignatureAssignabilityInInheritance6.js
+++ b/tests/baselines/reference/callSignatureAssignabilityInInheritance6.js
@@ -55,7 +55,11 @@ interface I9<T> extends A {
 // same as subtypingWithCallSignatures4 but using class type parameters instead of generic signatures
 // all are errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/callWithSpread.js b/tests/baselines/reference/callWithSpread.js
index 2bce24e4637..c5d6bbf2401 100644
--- a/tests/baselines/reference/callWithSpread.js
+++ b/tests/baselines/reference/callWithSpread.js
@@ -60,7 +60,11 @@ class D extends C {
 
 //// [callWithSpread.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/captureThisInSuperCall.js b/tests/baselines/reference/captureThisInSuperCall.js
index 1a1d5562531..062d50e8ad9 100644
--- a/tests/baselines/reference/captureThisInSuperCall.js
+++ b/tests/baselines/reference/captureThisInSuperCall.js
@@ -10,7 +10,11 @@ class B extends A {
 
 //// [captureThisInSuperCall.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/castingTuple.js b/tests/baselines/reference/castingTuple.js
index 331a61a6f78..4b45f444f54 100644
--- a/tests/baselines/reference/castingTuple.js
+++ b/tests/baselines/reference/castingTuple.js
@@ -34,7 +34,11 @@ t4[2] = 10;
 
 //// [castingTuple.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/chainedAssignment3.js b/tests/baselines/reference/chainedAssignment3.js
index 3bfe61f2664..6c8453c2348 100644
--- a/tests/baselines/reference/chainedAssignment3.js
+++ b/tests/baselines/reference/chainedAssignment3.js
@@ -24,7 +24,11 @@ a = b = new A();
 
 //// [chainedAssignment3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js b/tests/baselines/reference/chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js
index 59a4b8b12ce..769f74d39ae 100644
--- a/tests/baselines/reference/chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js
+++ b/tests/baselines/reference/chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js
@@ -21,7 +21,11 @@ class C extends B {
 
 //// [chainedCallsWithTypeParameterConstrainedToOtherTypeParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkForObjectTooStrict.js b/tests/baselines/reference/checkForObjectTooStrict.js
index 80f12196d0d..cd65885b152 100644
--- a/tests/baselines/reference/checkForObjectTooStrict.js
+++ b/tests/baselines/reference/checkForObjectTooStrict.js
@@ -33,7 +33,11 @@ class Baz extends Object {
 
 //// [checkForObjectTooStrict.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing1.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing1.js
index 006bdbf356f..fece927ea9c 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing1.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing1.js
@@ -12,7 +12,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing2.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing2.js
index 5c35d42ca4f..143514be551 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing2.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing2.js
@@ -12,7 +12,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing3.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing3.js
index 16b8181ac5d..a080d62434f 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing3.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing3.js
@@ -17,7 +17,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing4.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing4.js
index 9ac1fdaaa21..2309600b2b8 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing4.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing4.js
@@ -21,7 +21,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing5.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing5.js
index 6f8d7589163..cc3838fd40d 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing5.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing5.js
@@ -9,7 +9,11 @@ class Derived extends Based {
 
 //// [checkSuperCallBeforeThisAccessing5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing6.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing6.js
index 415bbb06501..e6183330d97 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing6.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing6.js
@@ -12,7 +12,11 @@ class Super extends Base {
 
 //// [checkSuperCallBeforeThisAccessing6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing7.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing7.js
index 39eea670c57..3040a118a75 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing7.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing7.js
@@ -11,7 +11,11 @@ class Super extends Base {
 
 //// [checkSuperCallBeforeThisAccessing7.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/checkSuperCallBeforeThisAccessing8.js b/tests/baselines/reference/checkSuperCallBeforeThisAccessing8.js
index ff1801d1f93..899128b6836 100644
--- a/tests/baselines/reference/checkSuperCallBeforeThisAccessing8.js
+++ b/tests/baselines/reference/checkSuperCallBeforeThisAccessing8.js
@@ -12,7 +12,11 @@ class Super extends Base {
 
 //// [checkSuperCallBeforeThisAccessing8.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/circularImportAlias.js b/tests/baselines/reference/circularImportAlias.js
index 49e1124b467..6f2d3213aeb 100644
--- a/tests/baselines/reference/circularImportAlias.js
+++ b/tests/baselines/reference/circularImportAlias.js
@@ -22,7 +22,11 @@ var c = new B.a.C();
 //// [circularImportAlias.js]
 // expected no error
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/circularTypeofWithFunctionModule.js b/tests/baselines/reference/circularTypeofWithFunctionModule.js
index aa2987725bd..92403f0cb6b 100644
--- a/tests/baselines/reference/circularTypeofWithFunctionModule.js
+++ b/tests/baselines/reference/circularTypeofWithFunctionModule.js
@@ -15,7 +15,11 @@ namespace maker {
 //// [circularTypeofWithFunctionModule.js]
 // Repro from #6072
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractConstructorAssignability.js b/tests/baselines/reference/classAbstractConstructorAssignability.js
index 20f3de041be..704ff554a00 100644
--- a/tests/baselines/reference/classAbstractConstructorAssignability.js
+++ b/tests/baselines/reference/classAbstractConstructorAssignability.js
@@ -16,7 +16,11 @@ new CC;
 
 //// [classAbstractConstructorAssignability.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractCrashedOnce.js b/tests/baselines/reference/classAbstractCrashedOnce.js
index 2037dbbc64f..107d8274369 100644
--- a/tests/baselines/reference/classAbstractCrashedOnce.js
+++ b/tests/baselines/reference/classAbstractCrashedOnce.js
@@ -12,7 +12,11 @@ var x = new bar();
 
 //// [classAbstractCrashedOnce.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractExtends.js b/tests/baselines/reference/classAbstractExtends.js
index d7e9a04d189..f9fa0ba2b32 100644
--- a/tests/baselines/reference/classAbstractExtends.js
+++ b/tests/baselines/reference/classAbstractExtends.js
@@ -18,7 +18,11 @@ class E extends B {
 
 //// [classAbstractExtends.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractFactoryFunction.js b/tests/baselines/reference/classAbstractFactoryFunction.js
index 71850654425..addb71da717 100644
--- a/tests/baselines/reference/classAbstractFactoryFunction.js
+++ b/tests/baselines/reference/classAbstractFactoryFunction.js
@@ -19,7 +19,11 @@ NewB(B);
 
 //// [classAbstractFactoryFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractGeneric.js b/tests/baselines/reference/classAbstractGeneric.js
index e5f5598c14c..486fe97f838 100644
--- a/tests/baselines/reference/classAbstractGeneric.js
+++ b/tests/baselines/reference/classAbstractGeneric.js
@@ -27,7 +27,11 @@ class G<T> extends A<T> {
 
 //// [classAbstractGeneric.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractInAModule.js b/tests/baselines/reference/classAbstractInAModule.js
index 5ff60d21ca9..4681a422c8d 100644
--- a/tests/baselines/reference/classAbstractInAModule.js
+++ b/tests/baselines/reference/classAbstractInAModule.js
@@ -9,7 +9,11 @@ new M.B;
 
 //// [classAbstractInAModule.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractInheritance.js b/tests/baselines/reference/classAbstractInheritance.js
index 90d8216647a..ebaef77181a 100644
--- a/tests/baselines/reference/classAbstractInheritance.js
+++ b/tests/baselines/reference/classAbstractInheritance.js
@@ -23,7 +23,11 @@ abstract class GG extends CC {}
 
 //// [classAbstractInheritance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractInstantiations1.js b/tests/baselines/reference/classAbstractInstantiations1.js
index 4c6ed144e0b..96a0c1207be 100644
--- a/tests/baselines/reference/classAbstractInstantiations1.js
+++ b/tests/baselines/reference/classAbstractInstantiations1.js
@@ -29,7 +29,11 @@ c = new B;
 // Calling new with (non)abstract classes.
 //
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractInstantiations2.js b/tests/baselines/reference/classAbstractInstantiations2.js
index e5b678ee715..3b93e78aebd 100644
--- a/tests/baselines/reference/classAbstractInstantiations2.js
+++ b/tests/baselines/reference/classAbstractInstantiations2.js
@@ -53,7 +53,11 @@ class H { // error -- not declared abstract
 
 //// [classAbstractInstantiations2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractOverrideWithAbstract.js b/tests/baselines/reference/classAbstractOverrideWithAbstract.js
index 0cf9c039b35..59cd1186ef9 100644
--- a/tests/baselines/reference/classAbstractOverrideWithAbstract.js
+++ b/tests/baselines/reference/classAbstractOverrideWithAbstract.js
@@ -25,7 +25,11 @@ class DD extends BB {
 
 //// [classAbstractOverrideWithAbstract.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractSuperCalls.js b/tests/baselines/reference/classAbstractSuperCalls.js
index 30c33822be9..c63b2673713 100644
--- a/tests/baselines/reference/classAbstractSuperCalls.js
+++ b/tests/baselines/reference/classAbstractSuperCalls.js
@@ -29,7 +29,11 @@ abstract class BB extends AA {
 
 //// [classAbstractSuperCalls.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractUsingAbstractMethod1.js b/tests/baselines/reference/classAbstractUsingAbstractMethod1.js
index 5aa616dcb7c..421f3278489 100644
--- a/tests/baselines/reference/classAbstractUsingAbstractMethod1.js
+++ b/tests/baselines/reference/classAbstractUsingAbstractMethod1.js
@@ -19,7 +19,11 @@ a.foo();
 
 //// [classAbstractUsingAbstractMethod1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classAbstractUsingAbstractMethods2.js b/tests/baselines/reference/classAbstractUsingAbstractMethods2.js
index 56aa3937772..397d5a3a411 100644
--- a/tests/baselines/reference/classAbstractUsingAbstractMethods2.js
+++ b/tests/baselines/reference/classAbstractUsingAbstractMethods2.js
@@ -29,7 +29,11 @@ class DD extends AA {
 
 //// [classAbstractUsingAbstractMethods2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classConstructorAccessibility2.js b/tests/baselines/reference/classConstructorAccessibility2.js
index eeff60323b7..6cbf33cddff 100644
--- a/tests/baselines/reference/classConstructorAccessibility2.js
+++ b/tests/baselines/reference/classConstructorAccessibility2.js
@@ -48,7 +48,11 @@ var dc = new DerivedC(1);
 
 //// [classConstructorAccessibility2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classConstructorAccessibility4.js b/tests/baselines/reference/classConstructorAccessibility4.js
index 199383b6a71..61ce64ef19b 100644
--- a/tests/baselines/reference/classConstructorAccessibility4.js
+++ b/tests/baselines/reference/classConstructorAccessibility4.js
@@ -32,7 +32,11 @@ class D {
 
 //// [classConstructorAccessibility4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classConstructorAccessibility5.js b/tests/baselines/reference/classConstructorAccessibility5.js
index cb01b233781..8d0f9ad4069 100644
--- a/tests/baselines/reference/classConstructorAccessibility5.js
+++ b/tests/baselines/reference/classConstructorAccessibility5.js
@@ -13,7 +13,11 @@ class Unrelated {
 
 //// [classConstructorAccessibility5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classConstructorParametersAccessibility.js b/tests/baselines/reference/classConstructorParametersAccessibility.js
index 4b086a854a1..2433a6d3934 100644
--- a/tests/baselines/reference/classConstructorParametersAccessibility.js
+++ b/tests/baselines/reference/classConstructorParametersAccessibility.js
@@ -28,7 +28,11 @@ class Derived extends C3 {
 
 //// [classConstructorParametersAccessibility.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classConstructorParametersAccessibility2.js b/tests/baselines/reference/classConstructorParametersAccessibility2.js
index 244b56dddc0..b29e3f06503 100644
--- a/tests/baselines/reference/classConstructorParametersAccessibility2.js
+++ b/tests/baselines/reference/classConstructorParametersAccessibility2.js
@@ -28,7 +28,11 @@ class Derived extends C3 {
 
 //// [classConstructorParametersAccessibility2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classConstructorParametersAccessibility3.js b/tests/baselines/reference/classConstructorParametersAccessibility3.js
index ef3e6d5b4bd..10031b9c74e 100644
--- a/tests/baselines/reference/classConstructorParametersAccessibility3.js
+++ b/tests/baselines/reference/classConstructorParametersAccessibility3.js
@@ -15,7 +15,11 @@ d.p;  // public, OK
 
 //// [classConstructorParametersAccessibility3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classDeclarationMergedInModuleWithContinuation.js b/tests/baselines/reference/classDeclarationMergedInModuleWithContinuation.js
index 1fa51632ba7..1521745f951 100644
--- a/tests/baselines/reference/classDeclarationMergedInModuleWithContinuation.js
+++ b/tests/baselines/reference/classDeclarationMergedInModuleWithContinuation.js
@@ -13,7 +13,11 @@ module M {
 
 //// [classDeclarationMergedInModuleWithContinuation.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classDeclaredBeforeClassFactory.js b/tests/baselines/reference/classDeclaredBeforeClassFactory.js
index c30c913a010..24df98a089f 100644
--- a/tests/baselines/reference/classDeclaredBeforeClassFactory.js
+++ b/tests/baselines/reference/classDeclaredBeforeClassFactory.js
@@ -9,7 +9,11 @@ function makeBaseClass() {
 
 //// [classDeclaredBeforeClassFactory.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classDoesNotDependOnBaseTypes.js b/tests/baselines/reference/classDoesNotDependOnBaseTypes.js
index e195506c294..88a1ab19d14 100644
--- a/tests/baselines/reference/classDoesNotDependOnBaseTypes.js
+++ b/tests/baselines/reference/classDoesNotDependOnBaseTypes.js
@@ -14,7 +14,11 @@ class StringTreeCollection extends StringTreeCollectionBase { }
 
 //// [classDoesNotDependOnBaseTypes.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExpression2.js b/tests/baselines/reference/classExpression2.js
index 7e78007badc..86d4509310d 100644
--- a/tests/baselines/reference/classExpression2.js
+++ b/tests/baselines/reference/classExpression2.js
@@ -4,7 +4,11 @@ var v = class C extends D {};
 
 //// [classExpression2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExpression3.js b/tests/baselines/reference/classExpression3.js
index 9c29f35cd19..0d999b57a1a 100644
--- a/tests/baselines/reference/classExpression3.js
+++ b/tests/baselines/reference/classExpression3.js
@@ -8,7 +8,11 @@ c.c;
 
 //// [classExpression3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExpressionExtendingAbstractClass.js b/tests/baselines/reference/classExpressionExtendingAbstractClass.js
index 3031f69117a..3c9db5e28ac 100644
--- a/tests/baselines/reference/classExpressionExtendingAbstractClass.js
+++ b/tests/baselines/reference/classExpressionExtendingAbstractClass.js
@@ -10,7 +10,11 @@ var C = class extends A {     // no error reported!
 
 //// [classExpressionExtendingAbstractClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingBuiltinType.js b/tests/baselines/reference/classExtendingBuiltinType.js
index c0988a01296..d2be7a12da2 100644
--- a/tests/baselines/reference/classExtendingBuiltinType.js
+++ b/tests/baselines/reference/classExtendingBuiltinType.js
@@ -13,7 +13,11 @@ class C10 extends Array<number> { }
 
 //// [classExtendingBuiltinType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingClass.js b/tests/baselines/reference/classExtendingClass.js
index 5b5a1386322..a81efb38bd0 100644
--- a/tests/baselines/reference/classExtendingClass.js
+++ b/tests/baselines/reference/classExtendingClass.js
@@ -33,7 +33,11 @@ var r8 = D2.other(1);
 
 //// [classExtendingClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingClassLikeType.js b/tests/baselines/reference/classExtendingClassLikeType.js
index 1d16866904e..7760490a244 100644
--- a/tests/baselines/reference/classExtendingClassLikeType.js
+++ b/tests/baselines/reference/classExtendingClassLikeType.js
@@ -60,7 +60,11 @@ class D5 extends getBadBase() {
 
 //// [classExtendingClassLikeType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingNonConstructor.js b/tests/baselines/reference/classExtendingNonConstructor.js
index 74070c3bc0c..d14663b4edc 100644
--- a/tests/baselines/reference/classExtendingNonConstructor.js
+++ b/tests/baselines/reference/classExtendingNonConstructor.js
@@ -16,7 +16,11 @@ class C7 extends foo { }
 
 //// [classExtendingNonConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingNull.js b/tests/baselines/reference/classExtendingNull.js
index 3a227b564e9..9ce3714c1bd 100644
--- a/tests/baselines/reference/classExtendingNull.js
+++ b/tests/baselines/reference/classExtendingNull.js
@@ -5,7 +5,11 @@ class C2 extends (null) { }
 
 //// [classExtendingNull.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingPrimitive.js b/tests/baselines/reference/classExtendingPrimitive.js
index 04fd2d57e52..9e1a855379c 100644
--- a/tests/baselines/reference/classExtendingPrimitive.js
+++ b/tests/baselines/reference/classExtendingPrimitive.js
@@ -17,7 +17,11 @@ class C8 extends E { }
 //// [classExtendingPrimitive.js]
 // classes cannot extend primitives
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingPrimitive2.js b/tests/baselines/reference/classExtendingPrimitive2.js
index a85bcb21f09..ff7f19fc68d 100644
--- a/tests/baselines/reference/classExtendingPrimitive2.js
+++ b/tests/baselines/reference/classExtendingPrimitive2.js
@@ -7,7 +7,11 @@ class C5a extends null { }
 //// [classExtendingPrimitive2.js]
 // classes cannot extend primitives
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingQualifiedName.js b/tests/baselines/reference/classExtendingQualifiedName.js
index 6c2d5b6c2e4..9a7d4551cf3 100644
--- a/tests/baselines/reference/classExtendingQualifiedName.js
+++ b/tests/baselines/reference/classExtendingQualifiedName.js
@@ -9,7 +9,11 @@ module M {
 
 //// [classExtendingQualifiedName.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendingQualifiedName2.js b/tests/baselines/reference/classExtendingQualifiedName2.js
index 946a7604ca4..adf590b6804 100644
--- a/tests/baselines/reference/classExtendingQualifiedName2.js
+++ b/tests/baselines/reference/classExtendingQualifiedName2.js
@@ -9,7 +9,11 @@ module M {
 
 //// [classExtendingQualifiedName2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsAcrossFiles.js b/tests/baselines/reference/classExtendsAcrossFiles.js
index 0fa873d378f..45598142549 100644
--- a/tests/baselines/reference/classExtendsAcrossFiles.js
+++ b/tests/baselines/reference/classExtendsAcrossFiles.js
@@ -22,7 +22,11 @@ export const b = {
 //// [b.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -47,7 +51,11 @@ exports.b = {
 //// [a.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsClauseClassMergedWithModuleNotReferingConstructor.js b/tests/baselines/reference/classExtendsClauseClassMergedWithModuleNotReferingConstructor.js
index b164b77d319..187108fcf54 100644
--- a/tests/baselines/reference/classExtendsClauseClassMergedWithModuleNotReferingConstructor.js
+++ b/tests/baselines/reference/classExtendsClauseClassMergedWithModuleNotReferingConstructor.js
@@ -15,7 +15,11 @@ module Foo {
 
 //// [classExtendsClauseClassMergedWithModuleNotReferingConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsClauseClassNotReferringConstructor.js b/tests/baselines/reference/classExtendsClauseClassNotReferringConstructor.js
index 619d1488ff8..4d63c45f2c9 100644
--- a/tests/baselines/reference/classExtendsClauseClassNotReferringConstructor.js
+++ b/tests/baselines/reference/classExtendsClauseClassNotReferringConstructor.js
@@ -8,7 +8,11 @@ module Foo {
 
 //// [classExtendsClauseClassNotReferringConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsEveryObjectType.js b/tests/baselines/reference/classExtendsEveryObjectType.js
index 044ef0fca51..e5b5651153c 100644
--- a/tests/baselines/reference/classExtendsEveryObjectType.js
+++ b/tests/baselines/reference/classExtendsEveryObjectType.js
@@ -18,7 +18,11 @@ class C6 extends []{ } // error
 
 //// [classExtendsEveryObjectType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsEveryObjectType2.js b/tests/baselines/reference/classExtendsEveryObjectType2.js
index 88929e72c57..9e935e789e4 100644
--- a/tests/baselines/reference/classExtendsEveryObjectType2.js
+++ b/tests/baselines/reference/classExtendsEveryObjectType2.js
@@ -5,7 +5,11 @@ class C6 extends []{ } // error
 
 //// [classExtendsEveryObjectType2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsInterface.js b/tests/baselines/reference/classExtendsInterface.js
index 1005ccbdd3f..68167082021 100644
--- a/tests/baselines/reference/classExtendsInterface.js
+++ b/tests/baselines/reference/classExtendsInterface.js
@@ -10,7 +10,11 @@ class B2<T> implements Comparable2<T> {}
 
 //// [classExtendsInterface.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsInterfaceInExpression.js b/tests/baselines/reference/classExtendsInterfaceInExpression.js
index 511d22e93f1..fa433e139c7 100644
--- a/tests/baselines/reference/classExtendsInterfaceInExpression.js
+++ b/tests/baselines/reference/classExtendsInterfaceInExpression.js
@@ -10,7 +10,11 @@ class C extends factory(A) {}
 
 //// [classExtendsInterfaceInExpression.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsInterfaceInModule.js b/tests/baselines/reference/classExtendsInterfaceInModule.js
index a3034d59df7..933c5162477 100644
--- a/tests/baselines/reference/classExtendsInterfaceInModule.js
+++ b/tests/baselines/reference/classExtendsInterfaceInModule.js
@@ -17,7 +17,11 @@ class D extends Mod.Nested.I {}
 
 //// [classExtendsInterfaceInModule.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsItself.js b/tests/baselines/reference/classExtendsItself.js
index ad4ce10cfc6..e13cd6dee6e 100644
--- a/tests/baselines/reference/classExtendsItself.js
+++ b/tests/baselines/reference/classExtendsItself.js
@@ -7,7 +7,11 @@ class E<T> extends E<string> { } // error
 
 //// [classExtendsItself.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsItselfIndirectly.js b/tests/baselines/reference/classExtendsItselfIndirectly.js
index dfbfb7720fa..bef7ca9f8cf 100644
--- a/tests/baselines/reference/classExtendsItselfIndirectly.js
+++ b/tests/baselines/reference/classExtendsItselfIndirectly.js
@@ -13,7 +13,11 @@ class E2<T> extends D2<T> { baz: T; }
 
 //// [classExtendsItselfIndirectly.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsItselfIndirectly2.js b/tests/baselines/reference/classExtendsItselfIndirectly2.js
index 6751b19335d..e9df1ddf908 100644
--- a/tests/baselines/reference/classExtendsItselfIndirectly2.js
+++ b/tests/baselines/reference/classExtendsItselfIndirectly2.js
@@ -24,7 +24,11 @@ module O {
 
 //// [classExtendsItselfIndirectly2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsItselfIndirectly3.js b/tests/baselines/reference/classExtendsItselfIndirectly3.js
index 750e5ddfd1c..a324fa1ce72 100644
--- a/tests/baselines/reference/classExtendsItselfIndirectly3.js
+++ b/tests/baselines/reference/classExtendsItselfIndirectly3.js
@@ -20,7 +20,11 @@ class E2<T> extends D2<T> { baz: T; }
 
 //// [classExtendsItselfIndirectly_file1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -33,7 +37,11 @@ var C = (function (_super) {
 }(E)); // error
 //// [classExtendsItselfIndirectly_file2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -46,7 +54,11 @@ var D = (function (_super) {
 }(C));
 //// [classExtendsItselfIndirectly_file3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -59,7 +71,11 @@ var E = (function (_super) {
 }(D));
 //// [classExtendsItselfIndirectly_file4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -72,7 +88,11 @@ var C2 = (function (_super) {
 }(E2)); // error
 //// [classExtendsItselfIndirectly_file5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -85,7 +105,11 @@ var D2 = (function (_super) {
 }(C2));
 //// [classExtendsItselfIndirectly_file6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsMultipleBaseClasses.js b/tests/baselines/reference/classExtendsMultipleBaseClasses.js
index 6cb987186c4..7cef2b247cc 100644
--- a/tests/baselines/reference/classExtendsMultipleBaseClasses.js
+++ b/tests/baselines/reference/classExtendsMultipleBaseClasses.js
@@ -5,7 +5,11 @@ class C extends A,B { }
 
 //// [classExtendsMultipleBaseClasses.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsNull.js b/tests/baselines/reference/classExtendsNull.js
index 45cd0132bda..5171dbc0085 100644
--- a/tests/baselines/reference/classExtendsNull.js
+++ b/tests/baselines/reference/classExtendsNull.js
@@ -14,7 +14,11 @@ class D extends null {
 
 //// [classExtendsNull.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsShadowedConstructorFunction.js b/tests/baselines/reference/classExtendsShadowedConstructorFunction.js
index fde420bca39..ad16e0aacaa 100644
--- a/tests/baselines/reference/classExtendsShadowedConstructorFunction.js
+++ b/tests/baselines/reference/classExtendsShadowedConstructorFunction.js
@@ -10,7 +10,11 @@ module M {
 
 //// [classExtendsShadowedConstructorFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classExtendsValidConstructorFunction.js b/tests/baselines/reference/classExtendsValidConstructorFunction.js
index 7346096d803..4e284b0c64c 100644
--- a/tests/baselines/reference/classExtendsValidConstructorFunction.js
+++ b/tests/baselines/reference/classExtendsValidConstructorFunction.js
@@ -7,7 +7,11 @@ class C extends foo { } // error, cannot extend it though
 
 //// [classExtendsValidConstructorFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classHeritageWithTrailingSeparator.js b/tests/baselines/reference/classHeritageWithTrailingSeparator.js
index ab37b45f3be..3314583f338 100644
--- a/tests/baselines/reference/classHeritageWithTrailingSeparator.js
+++ b/tests/baselines/reference/classHeritageWithTrailingSeparator.js
@@ -5,7 +5,11 @@ class D extends C, {
 
 //// [classHeritageWithTrailingSeparator.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classImplementsClass2.js b/tests/baselines/reference/classImplementsClass2.js
index 372f8ce84ef..0aeda35463f 100644
--- a/tests/baselines/reference/classImplementsClass2.js
+++ b/tests/baselines/reference/classImplementsClass2.js
@@ -15,7 +15,11 @@ c2 = c;
 
 //// [classImplementsClass2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classImplementsClass3.js b/tests/baselines/reference/classImplementsClass3.js
index 09c2a9fbe6b..40fd20005e1 100644
--- a/tests/baselines/reference/classImplementsClass3.js
+++ b/tests/baselines/reference/classImplementsClass3.js
@@ -16,7 +16,11 @@ c2 = c;
 
 //// [classImplementsClass3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classImplementsClass4.js b/tests/baselines/reference/classImplementsClass4.js
index c80e2152598..631b5b38560 100644
--- a/tests/baselines/reference/classImplementsClass4.js
+++ b/tests/baselines/reference/classImplementsClass4.js
@@ -18,7 +18,11 @@ c2 = c;
 
 //// [classImplementsClass4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classImplementsClass5.js b/tests/baselines/reference/classImplementsClass5.js
index de0bb4469e1..a54c02f4b6b 100644
--- a/tests/baselines/reference/classImplementsClass5.js
+++ b/tests/baselines/reference/classImplementsClass5.js
@@ -19,7 +19,11 @@ c2 = c;
 
 //// [classImplementsClass5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classImplementsClass6.js b/tests/baselines/reference/classImplementsClass6.js
index c87c1b59d2f..c2987ac066e 100644
--- a/tests/baselines/reference/classImplementsClass6.js
+++ b/tests/baselines/reference/classImplementsClass6.js
@@ -23,7 +23,11 @@ c2.bar(); // should error
 
 //// [classImplementsClass6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classIndexer3.js b/tests/baselines/reference/classIndexer3.js
index 759804baa41..8bce9236899 100644
--- a/tests/baselines/reference/classIndexer3.js
+++ b/tests/baselines/reference/classIndexer3.js
@@ -12,7 +12,11 @@ class D123 extends C123 {
 
 //// [classIndexer3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classInheritence.js b/tests/baselines/reference/classInheritence.js
index 614124c7a09..23506947e9b 100644
--- a/tests/baselines/reference/classInheritence.js
+++ b/tests/baselines/reference/classInheritence.js
@@ -4,7 +4,11 @@ class A extends A { }
 
 //// [classInheritence.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classIsSubtypeOfBaseType.js b/tests/baselines/reference/classIsSubtypeOfBaseType.js
index fe056e41813..df822eff312 100644
--- a/tests/baselines/reference/classIsSubtypeOfBaseType.js
+++ b/tests/baselines/reference/classIsSubtypeOfBaseType.js
@@ -17,7 +17,11 @@ class Derived2 extends Base<{ bar: string; }> {
 
 //// [classIsSubtypeOfBaseType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classOrder2.js b/tests/baselines/reference/classOrder2.js
index 34bbf93fd2f..d05dd72e245 100644
--- a/tests/baselines/reference/classOrder2.js
+++ b/tests/baselines/reference/classOrder2.js
@@ -21,7 +21,11 @@ a.foo();
 
 //// [classOrder2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classOrderBug.js b/tests/baselines/reference/classOrderBug.js
index 69ed7723a98..22596246d64 100644
--- a/tests/baselines/reference/classOrderBug.js
+++ b/tests/baselines/reference/classOrderBug.js
@@ -17,7 +17,11 @@ class foo extends baz {}
 
 //// [classOrderBug.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classSideInheritance1.js b/tests/baselines/reference/classSideInheritance1.js
index b3882d64b87..bdaaec468f8 100644
--- a/tests/baselines/reference/classSideInheritance1.js
+++ b/tests/baselines/reference/classSideInheritance1.js
@@ -17,7 +17,11 @@ C2.bar(); // valid
 
 //// [classSideInheritance1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classSideInheritance2.js b/tests/baselines/reference/classSideInheritance2.js
index 8a6564f4f9f..34c7467a864 100644
--- a/tests/baselines/reference/classSideInheritance2.js
+++ b/tests/baselines/reference/classSideInheritance2.js
@@ -22,7 +22,11 @@ class TextBase implements IText {
 
 //// [classSideInheritance2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classSideInheritance3.js b/tests/baselines/reference/classSideInheritance3.js
index 44035af4f30..a9fb0919930 100644
--- a/tests/baselines/reference/classSideInheritance3.js
+++ b/tests/baselines/reference/classSideInheritance3.js
@@ -20,7 +20,11 @@ var r3: typeof A = C; // ok
 
 //// [classSideInheritance3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classUpdateTests.js b/tests/baselines/reference/classUpdateTests.js
index d29277a84e4..89dd0bded24 100644
--- a/tests/baselines/reference/classUpdateTests.js
+++ b/tests/baselines/reference/classUpdateTests.js
@@ -115,7 +115,11 @@ class R {
 
 //// [classUpdateTests.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classWithBaseClassButNoConstructor.js b/tests/baselines/reference/classWithBaseClassButNoConstructor.js
index db10ddb0727..b23e0a13ba1 100644
--- a/tests/baselines/reference/classWithBaseClassButNoConstructor.js
+++ b/tests/baselines/reference/classWithBaseClassButNoConstructor.js
@@ -42,7 +42,11 @@ var d6 = new D(1); // ok
 
 //// [classWithBaseClassButNoConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classWithConstructors.js b/tests/baselines/reference/classWithConstructors.js
index 3e038e3a424..c3609f99b86 100644
--- a/tests/baselines/reference/classWithConstructors.js
+++ b/tests/baselines/reference/classWithConstructors.js
@@ -51,7 +51,11 @@ module Generics {
 
 //// [classWithConstructors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classWithProtectedProperty.js b/tests/baselines/reference/classWithProtectedProperty.js
index 35c26afef98..4a1b09ff350 100644
--- a/tests/baselines/reference/classWithProtectedProperty.js
+++ b/tests/baselines/reference/classWithProtectedProperty.js
@@ -30,7 +30,11 @@ class D extends C {
 //// [classWithProtectedProperty.js]
 // accessing any protected outside the class is an error
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classWithStaticMembers.js b/tests/baselines/reference/classWithStaticMembers.js
index 5deb8f99643..5563e859c6a 100644
--- a/tests/baselines/reference/classWithStaticMembers.js
+++ b/tests/baselines/reference/classWithStaticMembers.js
@@ -21,7 +21,11 @@ var r3 = r.foo;
 
 //// [classWithStaticMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/classdecl.js b/tests/baselines/reference/classdecl.js
index 99d7bba92b0..c88b0ccae0e 100644
--- a/tests/baselines/reference/classdecl.js
+++ b/tests/baselines/reference/classdecl.js
@@ -95,7 +95,11 @@ class e {
 
 //// [classdecl.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/clodulesDerivedClasses.js b/tests/baselines/reference/clodulesDerivedClasses.js
index 209b135fb15..1bb3fc7b705 100644
--- a/tests/baselines/reference/clodulesDerivedClasses.js
+++ b/tests/baselines/reference/clodulesDerivedClasses.js
@@ -24,7 +24,11 @@ module Path.Utils {
 
 //// [clodulesDerivedClasses.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js
index ec87855ba46..2242c6667a6 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js
@@ -41,7 +41,11 @@ class c extends Foo {
 
 //// [collisionSuperAndLocalFunctionInAccessors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js
index 09f1db5dd40..e761534649e 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js
@@ -26,7 +26,11 @@ class c extends Foo {
 
 //// [collisionSuperAndLocalFunctionInConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js
index 40084c7c2a5..70a9b22ddbd 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js
@@ -30,7 +30,11 @@ class c extends Foo {
 
 //// [collisionSuperAndLocalFunctionInMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js
index 457779fe395..258ad86c096 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js
@@ -20,7 +20,11 @@ class b extends Foo {
 
 //// [collisionSuperAndLocalFunctionInProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js b/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js
index 92a538bea04..81ef63068e6 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js
@@ -34,7 +34,11 @@ class c extends Foo {
 
 //// [collisionSuperAndLocalVarInAccessors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js b/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js
index c498658a974..355bf0af8af 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js
@@ -22,7 +22,11 @@ class c extends Foo {
 
 //// [collisionSuperAndLocalVarInConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js b/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js
index 94e42d35691..33512c60658 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js
@@ -20,7 +20,11 @@ class c extends Foo {
 
 //// [collisionSuperAndLocalVarInMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js b/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js
index 750de147841..ee582bddbc5 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js
@@ -19,7 +19,11 @@ class b extends Foo {
 
 //// [collisionSuperAndLocalVarInProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndNameResolution.js b/tests/baselines/reference/collisionSuperAndNameResolution.js
index dcfd4529266..e36a2a3cbad 100644
--- a/tests/baselines/reference/collisionSuperAndNameResolution.js
+++ b/tests/baselines/reference/collisionSuperAndNameResolution.js
@@ -13,7 +13,11 @@ class Foo extends base {
 
 //// [collisionSuperAndNameResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndParameter.js b/tests/baselines/reference/collisionSuperAndParameter.js
index 408158ba2a5..7413002635d 100644
--- a/tests/baselines/reference/collisionSuperAndParameter.js
+++ b/tests/baselines/reference/collisionSuperAndParameter.js
@@ -64,7 +64,11 @@ class Foo4 extends Foo {
 
 //// [collisionSuperAndParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndParameter1.js b/tests/baselines/reference/collisionSuperAndParameter1.js
index 58b1cbd4989..0a7e21e8ca2 100644
--- a/tests/baselines/reference/collisionSuperAndParameter1.js
+++ b/tests/baselines/reference/collisionSuperAndParameter1.js
@@ -11,7 +11,11 @@ class Foo2 extends Foo {
 
 //// [collisionSuperAndParameter1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js b/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js
index f6f38b6f099..5b12a0f9a9d 100644
--- a/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js
+++ b/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js
@@ -32,7 +32,11 @@ class b4 extends a {
 
 //// [collisionSuperAndPropertyNameAsConstuctorParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js
index 68707fd675d..d3270d4db57 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js
@@ -20,7 +20,11 @@ class b2 extends a {
 
 //// [collisionThisExpressionAndLocalVarWithSuperExperssion.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/commentsInheritance.js b/tests/baselines/reference/commentsInheritance.js
index a1e87482843..691854bffb0 100644
--- a/tests/baselines/reference/commentsInheritance.js
+++ b/tests/baselines/reference/commentsInheritance.js
@@ -153,7 +153,11 @@ i2_i = i3_i;
 
 //// [commentsInheritance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithIdenticalObjects.js b/tests/baselines/reference/comparisonOperatorWithIdenticalObjects.js
index 91482033255..3053f86f345 100644
--- a/tests/baselines/reference/comparisonOperatorWithIdenticalObjects.js
+++ b/tests/baselines/reference/comparisonOperatorWithIdenticalObjects.js
@@ -196,7 +196,11 @@ var r8b7 = b6 !== a6;
 
 //// [comparisonOperatorWithIdenticalObjects.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnCallSignature.js b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnCallSignature.js
index 95dfc215bfe..bf522a88367 100644
--- a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnCallSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnCallSignature.js
@@ -170,7 +170,11 @@ var r8b7 = b7 !== a7;
 
 //// [comparisonOperatorWithNoRelationshipObjectsOnCallSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnConstructorSignature.js b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnConstructorSignature.js
index fbcd4a72b99..50e31f1d79c 100644
--- a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnConstructorSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnConstructorSignature.js
@@ -170,7 +170,11 @@ var r8b7 = b7 !== a7;
 
 //// [comparisonOperatorWithNoRelationshipObjectsOnConstructorSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnIndexSignature.js b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnIndexSignature.js
index ec2e2556cc9..8e4e7e7840d 100644
--- a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnIndexSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnIndexSignature.js
@@ -113,7 +113,11 @@ var r8b4 = b4 !== a4;
 
 //// [comparisonOperatorWithNoRelationshipObjectsOnIndexSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedCallSignature.js b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedCallSignature.js
index 2e38deb0e55..f208bd500cd 100644
--- a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedCallSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedCallSignature.js
@@ -151,7 +151,11 @@ var r8b6 = b6 !== a6;
 
 //// [comparisonOperatorWithNoRelationshipObjectsOnInstantiatedCallSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedConstructorSignature.js b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedConstructorSignature.js
index 675cce7d49a..4cff1bf0584 100644
--- a/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedConstructorSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithNoRelationshipObjectsOnInstantiatedConstructorSignature.js
@@ -151,7 +151,11 @@ var r8b6 = b6 !== a6;
 
 //// [comparisonOperatorWithNoRelationshipObjectsOnInstantiatedConstructorSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js
index 634a6448581..0a7cbce0c32 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js
@@ -261,7 +261,11 @@ var r8b11 = b11 !== a11;
 
 //// [comparisonOperatorWithSubtypeObjectOnCallSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js
index d7857dcfd2a..bf8a6024faa 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js
@@ -223,7 +223,11 @@ var r8b9 = b9 !== a9;
 
 //// [comparisonOperatorWithSubtypeObjectOnConstructorSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnIndexSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnIndexSignature.js
index 08f08546aa9..f1e06f733e4 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnIndexSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnIndexSignature.js
@@ -109,7 +109,11 @@ var r8b1 = b4 !== a4;
 
 //// [comparisonOperatorWithSubtypeObjectOnIndexSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js
index ada0ee77486..78a7b456924 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js
@@ -166,7 +166,11 @@ var r8b6 = b6 !== a6;
 
 //// [comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js
index 28d960fc3c9..d08b7fbf11b 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js
@@ -166,7 +166,11 @@ var r8b6 = b6 !== a6;
 
 //// [comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnProperty.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnProperty.js
index 62fee91b7a3..d1f29b650c6 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnProperty.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnProperty.js
@@ -80,7 +80,11 @@ var rh4 = b2 !== a2;
 
 //// [comparisonOperatorWithSubtypeObjectOnProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/complexClassRelationships.js b/tests/baselines/reference/complexClassRelationships.js
index 3094d43eed2..34cc2754746 100644
--- a/tests/baselines/reference/complexClassRelationships.js
+++ b/tests/baselines/reference/complexClassRelationships.js
@@ -49,7 +49,11 @@ class FooBase {
 
 //// [complexClassRelationships.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/complicatedGenericRecursiveBaseClassReference.js b/tests/baselines/reference/complicatedGenericRecursiveBaseClassReference.js
index d9317789455..0e3dc9f3d31 100644
--- a/tests/baselines/reference/complicatedGenericRecursiveBaseClassReference.js
+++ b/tests/baselines/reference/complicatedGenericRecursiveBaseClassReference.js
@@ -7,7 +7,11 @@ class S18<B, A, C> extends S18<A[], { S19: A; (): A }[], C[]>
 
 //// [complicatedGenericRecursiveBaseClassReference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/compoundAssignmentLHSIsValue.js b/tests/baselines/reference/compoundAssignmentLHSIsValue.js
index a1f6274b38b..8d17fcbfe10 100644
--- a/tests/baselines/reference/compoundAssignmentLHSIsValue.js
+++ b/tests/baselines/reference/compoundAssignmentLHSIsValue.js
@@ -125,7 +125,11 @@ foo() += value;
 
 //// [compoundAssignmentLHSIsValue.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/compoundExponentiationAssignmentLHSIsValue.js b/tests/baselines/reference/compoundExponentiationAssignmentLHSIsValue.js
index 0c90b7b60f8..e7d1bef436e 100644
--- a/tests/baselines/reference/compoundExponentiationAssignmentLHSIsValue.js
+++ b/tests/baselines/reference/compoundExponentiationAssignmentLHSIsValue.js
@@ -87,7 +87,11 @@ foo() **= value;
 
 //// [compoundExponentiationAssignmentLHSIsValue.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames24_ES5.js b/tests/baselines/reference/computedPropertyNames24_ES5.js
index 03b7347165c..426b7cbaa65 100644
--- a/tests/baselines/reference/computedPropertyNames24_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames24_ES5.js
@@ -10,7 +10,11 @@ class C extends Base {
 
 //// [computedPropertyNames24_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames25_ES5.js b/tests/baselines/reference/computedPropertyNames25_ES5.js
index e98865176fb..239a5cada1a 100644
--- a/tests/baselines/reference/computedPropertyNames25_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames25_ES5.js
@@ -15,7 +15,11 @@ class C extends Base {
 
 //// [computedPropertyNames25_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames26_ES5.js b/tests/baselines/reference/computedPropertyNames26_ES5.js
index c10c3b112e4..89e8dd39169 100644
--- a/tests/baselines/reference/computedPropertyNames26_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames26_ES5.js
@@ -12,7 +12,11 @@ class C extends Base {
 
 //// [computedPropertyNames26_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames27_ES5.js b/tests/baselines/reference/computedPropertyNames27_ES5.js
index 0801b4b5e71..7438ea49fd2 100644
--- a/tests/baselines/reference/computedPropertyNames27_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames27_ES5.js
@@ -7,7 +7,11 @@ class C extends Base {
 
 //// [computedPropertyNames27_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames28_ES5.js b/tests/baselines/reference/computedPropertyNames28_ES5.js
index dc360dfd86a..132f811b49e 100644
--- a/tests/baselines/reference/computedPropertyNames28_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames28_ES5.js
@@ -12,7 +12,11 @@ class C extends Base {
 
 //// [computedPropertyNames28_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames30_ES5.js b/tests/baselines/reference/computedPropertyNames30_ES5.js
index 30c6fa33bbe..63e448df3c1 100644
--- a/tests/baselines/reference/computedPropertyNames30_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames30_ES5.js
@@ -17,7 +17,11 @@ class C extends Base {
 
 //// [computedPropertyNames30_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames31_ES5.js b/tests/baselines/reference/computedPropertyNames31_ES5.js
index 856fbe88f68..e3145b8c0a1 100644
--- a/tests/baselines/reference/computedPropertyNames31_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames31_ES5.js
@@ -17,7 +17,11 @@ class C extends Base {
 
 //// [computedPropertyNames31_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames43_ES5.js b/tests/baselines/reference/computedPropertyNames43_ES5.js
index ccc7aed3725..383da77c550 100644
--- a/tests/baselines/reference/computedPropertyNames43_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames43_ES5.js
@@ -14,7 +14,11 @@ class D extends C {
 
 //// [computedPropertyNames43_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames44_ES5.js b/tests/baselines/reference/computedPropertyNames44_ES5.js
index d16c7fc2f46..43bf2849333 100644
--- a/tests/baselines/reference/computedPropertyNames44_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames44_ES5.js
@@ -13,7 +13,11 @@ class D extends C {
 
 //// [computedPropertyNames44_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/computedPropertyNames45_ES5.js b/tests/baselines/reference/computedPropertyNames45_ES5.js
index 8585f28e5d6..933e6ea66ff 100644
--- a/tests/baselines/reference/computedPropertyNames45_ES5.js
+++ b/tests/baselines/reference/computedPropertyNames45_ES5.js
@@ -14,7 +14,11 @@ class D extends C {
 
 //// [computedPropertyNames45_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/conditionalOperatorWithIdenticalBCT.js b/tests/baselines/reference/conditionalOperatorWithIdenticalBCT.js
index 030fba2525b..c3a197e2a64 100644
--- a/tests/baselines/reference/conditionalOperatorWithIdenticalBCT.js
+++ b/tests/baselines/reference/conditionalOperatorWithIdenticalBCT.js
@@ -49,7 +49,11 @@ var result11: any = true ? 1 : 'string';
 
 //// [conditionalOperatorWithIdenticalBCT.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js b/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js
index 85633af2a25..0a1e2be65e9 100644
--- a/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js
+++ b/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js
@@ -25,7 +25,11 @@ var result61: (t: X) => number| string = true ? (m) => m.propertyX1 : (n) => n.p
 
 //// [conditionalOperatorWithoutIdenticalBCT.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constantOverloadFunction.js b/tests/baselines/reference/constantOverloadFunction.js
index 09e0c2788c4..05cb517f9e0 100644
--- a/tests/baselines/reference/constantOverloadFunction.js
+++ b/tests/baselines/reference/constantOverloadFunction.js
@@ -15,7 +15,11 @@ function foo(tagName: any): Base {
 
 //// [constantOverloadFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constantOverloadFunctionNoSubtypeError.js b/tests/baselines/reference/constantOverloadFunctionNoSubtypeError.js
index dd5bbf27d61..754abfd106e 100644
--- a/tests/baselines/reference/constantOverloadFunctionNoSubtypeError.js
+++ b/tests/baselines/reference/constantOverloadFunctionNoSubtypeError.js
@@ -16,7 +16,11 @@ function foo(tagName: any): Base {
 
 //// [constantOverloadFunctionNoSubtypeError.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constraintCheckInGenericBaseTypeReference.js b/tests/baselines/reference/constraintCheckInGenericBaseTypeReference.js
index a68f1411821..c1747ba54ff 100644
--- a/tests/baselines/reference/constraintCheckInGenericBaseTypeReference.js
+++ b/tests/baselines/reference/constraintCheckInGenericBaseTypeReference.js
@@ -21,7 +21,11 @@ class Container {
 
 //// [constraintCheckInGenericBaseTypeReference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructSignatureAssignabilityInInheritance2.js b/tests/baselines/reference/constructSignatureAssignabilityInInheritance2.js
index f082035064b..9b6d7599516 100644
--- a/tests/baselines/reference/constructSignatureAssignabilityInInheritance2.js
+++ b/tests/baselines/reference/constructSignatureAssignabilityInInheritance2.js
@@ -72,7 +72,11 @@ interface I extends A {
 //// [constructSignatureAssignabilityInInheritance2.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.js b/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.js
index ad834dd6cb4..c7b62f9521f 100644
--- a/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.js
+++ b/tests/baselines/reference/constructSignatureAssignabilityInInheritance3.js
@@ -115,7 +115,11 @@ module Errors {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // error cases
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructSignatureAssignabilityInInheritance4.js b/tests/baselines/reference/constructSignatureAssignabilityInInheritance4.js
index 12fc6bc872f..c328a70455f 100644
--- a/tests/baselines/reference/constructSignatureAssignabilityInInheritance4.js
+++ b/tests/baselines/reference/constructSignatureAssignabilityInInheritance4.js
@@ -62,7 +62,11 @@ interface I extends A {
 //// [constructSignatureAssignabilityInInheritance4.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructSignatureAssignabilityInInheritance5.js b/tests/baselines/reference/constructSignatureAssignabilityInInheritance5.js
index 10172a751ab..4f2addd338b 100644
--- a/tests/baselines/reference/constructSignatureAssignabilityInInheritance5.js
+++ b/tests/baselines/reference/constructSignatureAssignabilityInInheritance5.js
@@ -52,7 +52,11 @@ interface I extends B {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // same as subtypingWithConstructSignatures2 just with an extra level of indirection in the inheritance chain
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructSignatureAssignabilityInInheritance6.js b/tests/baselines/reference/constructSignatureAssignabilityInInheritance6.js
index 8c0fc83b406..a8bac464ac3 100644
--- a/tests/baselines/reference/constructSignatureAssignabilityInInheritance6.js
+++ b/tests/baselines/reference/constructSignatureAssignabilityInInheritance6.js
@@ -55,7 +55,11 @@ interface I9<T> extends A {
 // same as subtypingWithConstructSignatures4 but using class type parameters instead of generic signatures
 // all are errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorArgs.js b/tests/baselines/reference/constructorArgs.js
index 333cc843162..001a0656c91 100644
--- a/tests/baselines/reference/constructorArgs.js
+++ b/tests/baselines/reference/constructorArgs.js
@@ -17,7 +17,11 @@ class Sub extends Super {
 
 //// [constructorArgs.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType.js b/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType.js
index 806ff9581ca..4132399c970 100644
--- a/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType.js
+++ b/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType.js
@@ -21,7 +21,11 @@ class Derived2 extends Base {
 
 //// [constructorFunctionTypeIsAssignableToBaseType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType2.js b/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType2.js
index 4308710ef81..339edd29823 100644
--- a/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType2.js
+++ b/tests/baselines/reference/constructorFunctionTypeIsAssignableToBaseType2.js
@@ -35,7 +35,11 @@ class Derived2 extends Base {
 //// [constructorFunctionTypeIsAssignableToBaseType2.js]
 // the constructor function itself does not need to be a subtype of the base type constructor function
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorHasPrototypeProperty.js b/tests/baselines/reference/constructorHasPrototypeProperty.js
index c36307ee7fe..551b2644518 100644
--- a/tests/baselines/reference/constructorHasPrototypeProperty.js
+++ b/tests/baselines/reference/constructorHasPrototypeProperty.js
@@ -33,7 +33,11 @@ module Generic {
 
 //// [constructorHasPrototypeProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorOverloads2.js b/tests/baselines/reference/constructorOverloads2.js
index 43553c8f72c..5aca4c6583a 100644
--- a/tests/baselines/reference/constructorOverloads2.js
+++ b/tests/baselines/reference/constructorOverloads2.js
@@ -27,7 +27,11 @@ f1.bar1();
 
 //// [constructorOverloads2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorOverloads3.js b/tests/baselines/reference/constructorOverloads3.js
index fc916a1b283..063f4c72443 100644
--- a/tests/baselines/reference/constructorOverloads3.js
+++ b/tests/baselines/reference/constructorOverloads3.js
@@ -24,7 +24,11 @@ f1.bar1();
 
 //// [constructorOverloads3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorWithCapturedSuper.js b/tests/baselines/reference/constructorWithCapturedSuper.js
index f128a5f25a0..706d2522cfb 100644
--- a/tests/baselines/reference/constructorWithCapturedSuper.js
+++ b/tests/baselines/reference/constructorWithCapturedSuper.js
@@ -54,7 +54,11 @@ class D extends A {
 
 //// [constructorWithCapturedSuper.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/constructorWithIncompleteTypeAnnotation.js b/tests/baselines/reference/constructorWithIncompleteTypeAnnotation.js
index bcf6ee23d91..6c670b245c5 100644
--- a/tests/baselines/reference/constructorWithIncompleteTypeAnnotation.js
+++ b/tests/baselines/reference/constructorWithIncompleteTypeAnnotation.js
@@ -282,7 +282,11 @@ TypeScriptAllInOne.Program.Main();
 
 //// [constructorWithIncompleteTypeAnnotation.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/contextualTypingArrayOfLambdas.js b/tests/baselines/reference/contextualTypingArrayOfLambdas.js
index 6358453f4fa..9a172c202b2 100644
--- a/tests/baselines/reference/contextualTypingArrayOfLambdas.js
+++ b/tests/baselines/reference/contextualTypingArrayOfLambdas.js
@@ -16,7 +16,11 @@ var xs = [(x: A) => { }, (x: B) => { }, (x: C) => { }];
 
 //// [contextualTypingArrayOfLambdas.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/contextualTypingOfConditionalExpression.js b/tests/baselines/reference/contextualTypingOfConditionalExpression.js
index 70234ea3fec..c573962825b 100644
--- a/tests/baselines/reference/contextualTypingOfConditionalExpression.js
+++ b/tests/baselines/reference/contextualTypingOfConditionalExpression.js
@@ -16,7 +16,11 @@ var x2: (a: A) => void = true ? (a) => a.foo : (b) => b.foo;
 
 //// [contextualTypingOfConditionalExpression.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/contextualTypingOfConditionalExpression2.js b/tests/baselines/reference/contextualTypingOfConditionalExpression2.js
index 5c40163b2e0..9ee11aeb985 100644
--- a/tests/baselines/reference/contextualTypingOfConditionalExpression2.js
+++ b/tests/baselines/reference/contextualTypingOfConditionalExpression2.js
@@ -14,7 +14,11 @@ var x2: (a: A) => void = true ? (a: C) => a.foo : (b: number) => { };
 
 //// [contextualTypingOfConditionalExpression2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/crashInsourcePropertyIsRelatableToTargetProperty.js b/tests/baselines/reference/crashInsourcePropertyIsRelatableToTargetProperty.js
index 2afea65e32a..2d7ca989a81 100644
--- a/tests/baselines/reference/crashInsourcePropertyIsRelatableToTargetProperty.js
+++ b/tests/baselines/reference/crashInsourcePropertyIsRelatableToTargetProperty.js
@@ -12,7 +12,11 @@ var a: D = foo("hi", []);
 
 //// [crashInsourcePropertyIsRelatableToTargetProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileClassExtendsNull.js b/tests/baselines/reference/declFileClassExtendsNull.js
index 0638373ab22..483c1ca4481 100644
--- a/tests/baselines/reference/declFileClassExtendsNull.js
+++ b/tests/baselines/reference/declFileClassExtendsNull.js
@@ -5,7 +5,11 @@ class ExtendsNull extends null {
 
 //// [declFileClassExtendsNull.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileForFunctionTypeAsTypeParameter.js b/tests/baselines/reference/declFileForFunctionTypeAsTypeParameter.js
index 889ab313c01..f7465149b92 100644
--- a/tests/baselines/reference/declFileForFunctionTypeAsTypeParameter.js
+++ b/tests/baselines/reference/declFileForFunctionTypeAsTypeParameter.js
@@ -11,7 +11,11 @@ interface I extends X<() => number> {
 
 //// [declFileForFunctionTypeAsTypeParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileGenericClassWithGenericExtendedClass.js b/tests/baselines/reference/declFileGenericClassWithGenericExtendedClass.js
index 005e33950bc..8d0e10f73f9 100644
--- a/tests/baselines/reference/declFileGenericClassWithGenericExtendedClass.js
+++ b/tests/baselines/reference/declFileGenericClassWithGenericExtendedClass.js
@@ -14,7 +14,11 @@ class Baz implements IBar<Baz> {
 
 //// [declFileGenericClassWithGenericExtendedClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileGenericType.js b/tests/baselines/reference/declFileGenericType.js
index 47af8dc415a..f579968df06 100644
--- a/tests/baselines/reference/declFileGenericType.js
+++ b/tests/baselines/reference/declFileGenericType.js
@@ -42,7 +42,11 @@ export var j = C.F6;
 //// [declFileGenericType.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileGenericType2.js b/tests/baselines/reference/declFileGenericType2.js
index f6fb93cb28b..4f01f058b19 100644
--- a/tests/baselines/reference/declFileGenericType2.js
+++ b/tests/baselines/reference/declFileGenericType2.js
@@ -44,7 +44,11 @@ module templa.dom.mvc.composite {
 
 //// [declFileGenericType2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileWithClassNameConflictingWithClassReferredByExtendsClause.js b/tests/baselines/reference/declFileWithClassNameConflictingWithClassReferredByExtendsClause.js
index 45cde43ee4f..8f38d09160f 100644
--- a/tests/baselines/reference/declFileWithClassNameConflictingWithClassReferredByExtendsClause.js
+++ b/tests/baselines/reference/declFileWithClassNameConflictingWithClassReferredByExtendsClause.js
@@ -22,7 +22,11 @@ module X.Y.base.Z {
 
 //// [declFileWithClassNameConflictingWithClassReferredByExtendsClause.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declFileWithExtendsClauseThatHasItsContainerNameConflict.js b/tests/baselines/reference/declFileWithExtendsClauseThatHasItsContainerNameConflict.js
index c7b4a7483e9..cacaa587609 100644
--- a/tests/baselines/reference/declFileWithExtendsClauseThatHasItsContainerNameConflict.js
+++ b/tests/baselines/reference/declFileWithExtendsClauseThatHasItsContainerNameConflict.js
@@ -20,7 +20,11 @@ module A.B.C {
 
 //// [declFileWithExtendsClauseThatHasItsContainerNameConflict.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends.js b/tests/baselines/reference/declarationEmitExpressionInExtends.js
index 34b8206e43a..acda2589195 100644
--- a/tests/baselines/reference/declarationEmitExpressionInExtends.js
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends.js
@@ -16,7 +16,11 @@ q.s;
 
 //// [declarationEmitExpressionInExtends.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends2.js b/tests/baselines/reference/declarationEmitExpressionInExtends2.js
index 106fe00152b..8f0c53f66ac 100644
--- a/tests/baselines/reference/declarationEmitExpressionInExtends2.js
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends2.js
@@ -14,7 +14,11 @@ class MyClass extends getClass(2) <string, number> {
 
 //// [declarationEmitExpressionInExtends2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends3.js b/tests/baselines/reference/declarationEmitExpressionInExtends3.js
index c1fbd1fea90..902ddc08bc0 100644
--- a/tests/baselines/reference/declarationEmitExpressionInExtends3.js
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends3.js
@@ -46,7 +46,11 @@ export class MyClass4 extends getExportedClass<LocalInterface>(undefined)<Export
 //// [declarationEmitExpressionInExtends3.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends4.js b/tests/baselines/reference/declarationEmitExpressionInExtends4.js
index 08508b967c2..e9d107b3aa3 100644
--- a/tests/baselines/reference/declarationEmitExpressionInExtends4.js
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends4.js
@@ -19,7 +19,11 @@ class C3 extends SomeUndefinedFunction {
 
 //// [declarationEmitExpressionInExtends4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitNameConflicts3.js b/tests/baselines/reference/declarationEmitNameConflicts3.js
index 37cacfbc14b..38212cc5a86 100644
--- a/tests/baselines/reference/declarationEmitNameConflicts3.js
+++ b/tests/baselines/reference/declarationEmitNameConflicts3.js
@@ -28,7 +28,11 @@ module M.P {
 
 //// [declarationEmitNameConflicts3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitProtectedMembers.js b/tests/baselines/reference/declarationEmitProtectedMembers.js
index 56f1c5a1eb7..5f00d18b127 100644
--- a/tests/baselines/reference/declarationEmitProtectedMembers.js
+++ b/tests/baselines/reference/declarationEmitProtectedMembers.js
@@ -52,7 +52,11 @@ class C4 {
 
 //// [declarationEmitProtectedMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitThisPredicates01.js b/tests/baselines/reference/declarationEmitThisPredicates01.js
index cc1acaaa206..ac37811f017 100644
--- a/tests/baselines/reference/declarationEmitThisPredicates01.js
+++ b/tests/baselines/reference/declarationEmitThisPredicates01.js
@@ -12,7 +12,11 @@ export class D extends C {
 //// [declarationEmitThisPredicates01.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declarationEmitThisPredicatesWithPrivateName01.js b/tests/baselines/reference/declarationEmitThisPredicatesWithPrivateName01.js
index d449f0ec4fb..569c5997770 100644
--- a/tests/baselines/reference/declarationEmitThisPredicatesWithPrivateName01.js
+++ b/tests/baselines/reference/declarationEmitThisPredicatesWithPrivateName01.js
@@ -12,7 +12,11 @@ class D extends C {
 //// [declarationEmitThisPredicatesWithPrivateName01.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/declareDottedExtend.js b/tests/baselines/reference/declareDottedExtend.js
index 78ce534a8dd..91b00f923d1 100644
--- a/tests/baselines/reference/declareDottedExtend.js
+++ b/tests/baselines/reference/declareDottedExtend.js
@@ -13,7 +13,11 @@ class E extends A.B.C{ }
 
 //// [declareDottedExtend.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/decoratorOnClassConstructor2.js b/tests/baselines/reference/decoratorOnClassConstructor2.js
index dc0e7984f85..251edb39c2b 100644
--- a/tests/baselines/reference/decoratorOnClassConstructor2.js
+++ b/tests/baselines/reference/decoratorOnClassConstructor2.js
@@ -27,7 +27,11 @@ exports.foo = foo;
 //// [2.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/decoratorOnClassConstructor3.js b/tests/baselines/reference/decoratorOnClassConstructor3.js
index 4208665f033..f4a144837bf 100644
--- a/tests/baselines/reference/decoratorOnClassConstructor3.js
+++ b/tests/baselines/reference/decoratorOnClassConstructor3.js
@@ -29,7 +29,11 @@ exports.foo = foo;
 //// [2.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/decoratorOnClassMethod12.js b/tests/baselines/reference/decoratorOnClassMethod12.js
index 62361a40682..1c6c837660f 100644
--- a/tests/baselines/reference/decoratorOnClassMethod12.js
+++ b/tests/baselines/reference/decoratorOnClassMethod12.js
@@ -11,7 +11,11 @@ module M {
 
 //// [decoratorOnClassMethod12.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js b/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js
index 258a1cce825..f70f420b644 100644
--- a/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js
+++ b/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js
@@ -36,7 +36,11 @@ class D extends C {
 
 //// [derivedClassConstructorWithExplicitReturns01.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js.map b/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js.map
index 8b9037e40c9..d9c47863e53 100644
--- a/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js.map
+++ b/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.js.map
@@ -1,2 +1,2 @@
 //// [derivedClassConstructorWithExplicitReturns01.js.map]
-{"version":3,"file":"derivedClassConstructorWithExplicitReturns01.js","sourceRoot":"","sources":["derivedClassConstructorWithExplicitReturns01.ts"],"names":[],"mappings":";;;;;AACA;IAKI,WAAY,KAAa;QAJzB,UAAK,GAAG,EAAE,CAAC;QAKP,MAAM,CAAC;YACH,KAAK,EAAE,KAAK;YACZ,GAAG;gBACC,MAAM,CAAC,8BAA8B,CAAC;YAC1C,CAAC;SACJ,CAAA;IACL,CAAC;IATD,eAAG,GAAH,cAAQ,MAAM,CAAC,uBAAuB,CAAC,CAAC,CAAC;IAU7C,QAAC;AAAD,CAAC,AAbD,IAaC;AAED;IAAgB,qBAAC;IAGb,WAAY,CAAO;QAAP,kBAAA,EAAA,OAAO;QAAnB,YACI,kBAAM,CAAC,CAAC,SAYX;QAfD,WAAK,GAAG,cAAM,OAAA,KAAI,EAAJ,CAAI,CAAC;QAKf,EAAE,CAAC,CAAC,IAAI,CAAC,MAAM,EAAE,GAAG,GAAG,CAAC,CAAC,CAAC;YACtB,UAAU,CAAA;YACV,MAAM,CAAC;gBACH,KAAK,EAAE,CAAC;gBACR,KAAK,EAAE,cAAM,OAAA,KAAI,EAAJ,CAAI;gBACjB,GAAG,gBAAK,MAAM,CAAC,cAAc,CAAA,CAAC,CAAC;aAClC,CAAC;QACN,CAAC;QACD,IAAI;YACA,MAAM,CAAC,IAAI,CAAC;IACpB,CAAC;IACL,QAAC;AAAD,CAAC,AAjBD,CAAgB,CAAC,GAiBhB"}
\ No newline at end of file
+{"version":3,"file":"derivedClassConstructorWithExplicitReturns01.js","sourceRoot":"","sources":["derivedClassConstructorWithExplicitReturns01.ts"],"names":[],"mappings":";;;;;;;;;AACA;IAKI,WAAY,KAAa;QAJzB,UAAK,GAAG,EAAE,CAAC;QAKP,MAAM,CAAC;YACH,KAAK,EAAE,KAAK;YACZ,GAAG;gBACC,MAAM,CAAC,8BAA8B,CAAC;YAC1C,CAAC;SACJ,CAAA;IACL,CAAC;IATD,eAAG,GAAH,cAAQ,MAAM,CAAC,uBAAuB,CAAC,CAAC,CAAC;IAU7C,QAAC;AAAD,CAAC,AAbD,IAaC;AAED;IAAgB,qBAAC;IAGb,WAAY,CAAO;QAAP,kBAAA,EAAA,OAAO;QAAnB,YACI,kBAAM,CAAC,CAAC,SAYX;QAfD,WAAK,GAAG,cAAM,OAAA,KAAI,EAAJ,CAAI,CAAC;QAKf,EAAE,CAAC,CAAC,IAAI,CAAC,MAAM,EAAE,GAAG,GAAG,CAAC,CAAC,CAAC;YACtB,UAAU,CAAA;YACV,MAAM,CAAC;gBACH,KAAK,EAAE,CAAC;gBACR,KAAK,EAAE,cAAM,OAAA,KAAI,EAAJ,CAAI;gBACjB,GAAG,gBAAK,MAAM,CAAC,cAAc,CAAA,CAAC,CAAC;aAClC,CAAC;QACN,CAAC;QACD,IAAI;YACA,MAAM,CAAC,IAAI,CAAC;IACpB,CAAC;IACL,QAAC;AAAD,CAAC,AAjBD,CAAgB,CAAC,GAiBhB"}
\ No newline at end of file
diff --git a/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.sourcemap.txt b/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.sourcemap.txt
index d2b9e16ff7c..f363d82d836 100644
--- a/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.sourcemap.txt
+++ b/tests/baselines/reference/derivedClassConstructorWithExplicitReturns01.sourcemap.txt
@@ -9,7 +9,11 @@ emittedFile:tests/cases/compiler/derivedClassConstructorWithExplicitReturns01.js
 sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 -------------------------------------------------------------------
 >>>var __extends = (this && this.__extends) || function (d, b) {
->>>    Object.setPrototypeOf(d, b);
+>>>    if (typeof Object.setPrototypeOf === "function") {
+>>>        Object.setPrototypeOf(d, b);
+>>>    } else {
+>>>        d.__proto__ = b;
+>>>    }
 >>>    function __() { this.constructor = d; }
 >>>    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 >>>};
@@ -18,7 +22,7 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 2 >^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
   >
-1 >Emitted(6, 1) Source(2, 1) + SourceIndex(0)
+1 >Emitted(10, 1) Source(2, 1) + SourceIndex(0)
 ---
 >>>    function C(value) {
 1->^^^^
@@ -33,9 +37,9 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >    
 2 >    constructor(
 3 >               value: number
-1->Emitted(7, 5) Source(7, 5) + SourceIndex(0)
-2 >Emitted(7, 16) Source(7, 17) + SourceIndex(0)
-3 >Emitted(7, 21) Source(7, 30) + SourceIndex(0)
+1->Emitted(11, 5) Source(7, 5) + SourceIndex(0)
+2 >Emitted(11, 16) Source(7, 17) + SourceIndex(0)
+3 >Emitted(11, 21) Source(7, 30) + SourceIndex(0)
 ---
 >>>        this.cProp = 10;
 1->^^^^^^^^
@@ -48,11 +52,11 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 3 >                   = 
 4 >                     10
 5 >                       ;
-1->Emitted(8, 9) Source(3, 5) + SourceIndex(0)
-2 >Emitted(8, 19) Source(3, 10) + SourceIndex(0)
-3 >Emitted(8, 22) Source(3, 13) + SourceIndex(0)
-4 >Emitted(8, 24) Source(3, 15) + SourceIndex(0)
-5 >Emitted(8, 25) Source(3, 16) + SourceIndex(0)
+1->Emitted(12, 9) Source(3, 5) + SourceIndex(0)
+2 >Emitted(12, 19) Source(3, 10) + SourceIndex(0)
+3 >Emitted(12, 22) Source(3, 13) + SourceIndex(0)
+4 >Emitted(12, 24) Source(3, 15) + SourceIndex(0)
+5 >Emitted(12, 25) Source(3, 16) + SourceIndex(0)
 ---
 >>>        return {
 1 >^^^^^^^^
@@ -67,9 +71,9 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >        
 2 >        return
 3 >               
-1 >Emitted(9, 9) Source(8, 9) + SourceIndex(0)
-2 >Emitted(9, 15) Source(8, 15) + SourceIndex(0)
-3 >Emitted(9, 16) Source(8, 16) + SourceIndex(0)
+1 >Emitted(13, 9) Source(8, 9) + SourceIndex(0)
+2 >Emitted(13, 15) Source(8, 15) + SourceIndex(0)
+3 >Emitted(13, 16) Source(8, 16) + SourceIndex(0)
 ---
 >>>            cProp: value,
 1->^^^^^^^^^^^^
@@ -82,10 +86,10 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 2 >            cProp
 3 >                 : 
 4 >                   value
-1->Emitted(10, 13) Source(9, 13) + SourceIndex(0)
-2 >Emitted(10, 18) Source(9, 18) + SourceIndex(0)
-3 >Emitted(10, 20) Source(9, 20) + SourceIndex(0)
-4 >Emitted(10, 25) Source(9, 25) + SourceIndex(0)
+1->Emitted(14, 13) Source(9, 13) + SourceIndex(0)
+2 >Emitted(14, 18) Source(9, 18) + SourceIndex(0)
+3 >Emitted(14, 20) Source(9, 20) + SourceIndex(0)
+4 >Emitted(14, 25) Source(9, 25) + SourceIndex(0)
 ---
 >>>            foo: function () {
 1->^^^^^^^^^^^^
@@ -94,8 +98,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1->,
   >            
 2 >            foo
-1->Emitted(11, 13) Source(10, 13) + SourceIndex(0)
-2 >Emitted(11, 16) Source(10, 16) + SourceIndex(0)
+1->Emitted(15, 13) Source(10, 13) + SourceIndex(0)
+2 >Emitted(15, 16) Source(10, 16) + SourceIndex(0)
 ---
 >>>                return "well this looks kinda C-ish.";
 1->^^^^^^^^^^^^^^^^
@@ -109,11 +113,11 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 3 >                       
 4 >                       "well this looks kinda C-ish."
 5 >                                                     ;
-1->Emitted(12, 17) Source(11, 17) + SourceIndex(0)
-2 >Emitted(12, 23) Source(11, 23) + SourceIndex(0)
-3 >Emitted(12, 24) Source(11, 24) + SourceIndex(0)
-4 >Emitted(12, 54) Source(11, 54) + SourceIndex(0)
-5 >Emitted(12, 55) Source(11, 55) + SourceIndex(0)
+1->Emitted(16, 17) Source(11, 17) + SourceIndex(0)
+2 >Emitted(16, 23) Source(11, 23) + SourceIndex(0)
+3 >Emitted(16, 24) Source(11, 24) + SourceIndex(0)
+4 >Emitted(16, 54) Source(11, 54) + SourceIndex(0)
+5 >Emitted(16, 55) Source(11, 55) + SourceIndex(0)
 ---
 >>>            }
 1 >^^^^^^^^^^^^
@@ -121,8 +125,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1 >
   >            
 2 >            }
-1 >Emitted(13, 13) Source(12, 13) + SourceIndex(0)
-2 >Emitted(13, 14) Source(12, 14) + SourceIndex(0)
+1 >Emitted(17, 13) Source(12, 13) + SourceIndex(0)
+2 >Emitted(17, 14) Source(12, 14) + SourceIndex(0)
 ---
 >>>        };
 1 >^^^^^^^^^
@@ -130,8 +134,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1 >
   >        }
 2 >         
-1 >Emitted(14, 10) Source(13, 10) + SourceIndex(0)
-2 >Emitted(14, 11) Source(13, 10) + SourceIndex(0)
+1 >Emitted(18, 10) Source(13, 10) + SourceIndex(0)
+2 >Emitted(18, 11) Source(13, 10) + SourceIndex(0)
 ---
 >>>    }
 1 >^^^^
@@ -140,8 +144,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1 >
   >    
 2 >    }
-1 >Emitted(15, 5) Source(14, 5) + SourceIndex(0)
-2 >Emitted(15, 6) Source(14, 6) + SourceIndex(0)
+1 >Emitted(19, 5) Source(14, 5) + SourceIndex(0)
+2 >Emitted(19, 6) Source(14, 6) + SourceIndex(0)
 ---
 >>>    C.prototype.foo = function () { return "this never gets used."; };
 1->^^^^
@@ -164,16 +168,16 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 8 >                                                                  ;
 9 >                                                                    
 10>                                                                    }
-1->Emitted(16, 5) Source(5, 5) + SourceIndex(0)
-2 >Emitted(16, 20) Source(5, 8) + SourceIndex(0)
-3 >Emitted(16, 23) Source(5, 5) + SourceIndex(0)
-4 >Emitted(16, 37) Source(5, 13) + SourceIndex(0)
-5 >Emitted(16, 43) Source(5, 19) + SourceIndex(0)
-6 >Emitted(16, 44) Source(5, 20) + SourceIndex(0)
-7 >Emitted(16, 67) Source(5, 43) + SourceIndex(0)
-8 >Emitted(16, 68) Source(5, 44) + SourceIndex(0)
-9 >Emitted(16, 69) Source(5, 45) + SourceIndex(0)
-10>Emitted(16, 70) Source(5, 46) + SourceIndex(0)
+1->Emitted(20, 5) Source(5, 5) + SourceIndex(0)
+2 >Emitted(20, 20) Source(5, 8) + SourceIndex(0)
+3 >Emitted(20, 23) Source(5, 5) + SourceIndex(0)
+4 >Emitted(20, 37) Source(5, 13) + SourceIndex(0)
+5 >Emitted(20, 43) Source(5, 19) + SourceIndex(0)
+6 >Emitted(20, 44) Source(5, 20) + SourceIndex(0)
+7 >Emitted(20, 67) Source(5, 43) + SourceIndex(0)
+8 >Emitted(20, 68) Source(5, 44) + SourceIndex(0)
+9 >Emitted(20, 69) Source(5, 45) + SourceIndex(0)
+10>Emitted(20, 70) Source(5, 46) + SourceIndex(0)
 ---
 >>>    return C;
 1 >^^^^
@@ -190,8 +194,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >    }
   >
 2 >    }
-1 >Emitted(17, 5) Source(15, 1) + SourceIndex(0)
-2 >Emitted(17, 13) Source(15, 2) + SourceIndex(0)
+1 >Emitted(21, 5) Source(15, 1) + SourceIndex(0)
+2 >Emitted(21, 13) Source(15, 2) + SourceIndex(0)
 ---
 >>>}());
 1 >
@@ -216,10 +220,10 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >         }
   >     }
   > }
-1 >Emitted(18, 1) Source(15, 1) + SourceIndex(0)
-2 >Emitted(18, 2) Source(15, 2) + SourceIndex(0)
-3 >Emitted(18, 2) Source(2, 1) + SourceIndex(0)
-4 >Emitted(18, 6) Source(15, 2) + SourceIndex(0)
+1 >Emitted(22, 1) Source(15, 1) + SourceIndex(0)
+2 >Emitted(22, 2) Source(15, 2) + SourceIndex(0)
+3 >Emitted(22, 2) Source(2, 1) + SourceIndex(0)
+4 >Emitted(22, 6) Source(15, 2) + SourceIndex(0)
 ---
 >>>var D = (function (_super) {
 1->
@@ -227,15 +231,15 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1->
   >
   >
-1->Emitted(19, 1) Source(17, 1) + SourceIndex(0)
+1->Emitted(23, 1) Source(17, 1) + SourceIndex(0)
 ---
 >>>    __extends(D, _super);
 1->^^^^
 2 >    ^^^^^^^^^^^^^^^^^^^^^
 1->class D extends 
 2 >    C
-1->Emitted(20, 5) Source(17, 17) + SourceIndex(0)
-2 >Emitted(20, 26) Source(17, 18) + SourceIndex(0)
+1->Emitted(24, 5) Source(17, 17) + SourceIndex(0)
+2 >Emitted(24, 26) Source(17, 18) + SourceIndex(0)
 ---
 >>>    function D(a) {
 1 >^^^^
@@ -248,9 +252,9 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >    
 2 >    constructor(
 3 >               a = 100
-1 >Emitted(21, 5) Source(20, 5) + SourceIndex(0)
-2 >Emitted(21, 16) Source(20, 17) + SourceIndex(0)
-3 >Emitted(21, 17) Source(20, 24) + SourceIndex(0)
+1 >Emitted(25, 5) Source(20, 5) + SourceIndex(0)
+2 >Emitted(25, 16) Source(20, 17) + SourceIndex(0)
+3 >Emitted(25, 17) Source(20, 24) + SourceIndex(0)
 ---
 >>>        if (a === void 0) { a = 100; }
 1->^^^^^^^^
@@ -262,10 +266,10 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 2 >        
 3 >                          
 4 >                            a = 100
-1->Emitted(22, 9) Source(20, 17) + SourceIndex(0)
-2 >Emitted(22, 27) Source(20, 17) + SourceIndex(0)
-3 >Emitted(22, 29) Source(20, 17) + SourceIndex(0)
-4 >Emitted(22, 36) Source(20, 24) + SourceIndex(0)
+1->Emitted(26, 9) Source(20, 17) + SourceIndex(0)
+2 >Emitted(26, 27) Source(20, 17) + SourceIndex(0)
+3 >Emitted(26, 29) Source(20, 17) + SourceIndex(0)
+4 >Emitted(26, 36) Source(20, 24) + SourceIndex(0)
 ---
 >>>        var _this = _super.call(this, a) || this;
 1->^^^^^^^^
@@ -294,12 +298,12 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >                                                else
   >                                                    return null;
   >                                            }
-1->Emitted(23, 9) Source(20, 5) + SourceIndex(0)
-2 >Emitted(23, 21) Source(21, 9) + SourceIndex(0)
-3 >Emitted(23, 39) Source(21, 15) + SourceIndex(0)
-4 >Emitted(23, 40) Source(21, 16) + SourceIndex(0)
-5 >Emitted(23, 41) Source(21, 17) + SourceIndex(0)
-6 >Emitted(23, 50) Source(33, 6) + SourceIndex(0)
+1->Emitted(27, 9) Source(20, 5) + SourceIndex(0)
+2 >Emitted(27, 21) Source(21, 9) + SourceIndex(0)
+3 >Emitted(27, 39) Source(21, 15) + SourceIndex(0)
+4 >Emitted(27, 40) Source(21, 16) + SourceIndex(0)
+5 >Emitted(27, 41) Source(21, 17) + SourceIndex(0)
+6 >Emitted(27, 50) Source(33, 6) + SourceIndex(0)
 ---
 >>>        _this.dProp = function () { return _this; };
 1->^^^^^^^^
@@ -320,15 +324,15 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 7 >                                                
 8 >                                                  this
 9 >                                                   ;
-1->Emitted(24, 9) Source(18, 5) + SourceIndex(0)
-2 >Emitted(24, 20) Source(18, 10) + SourceIndex(0)
-3 >Emitted(24, 23) Source(18, 13) + SourceIndex(0)
-4 >Emitted(24, 37) Source(18, 19) + SourceIndex(0)
-5 >Emitted(24, 44) Source(18, 19) + SourceIndex(0)
-6 >Emitted(24, 49) Source(18, 23) + SourceIndex(0)
-7 >Emitted(24, 51) Source(18, 19) + SourceIndex(0)
-8 >Emitted(24, 52) Source(18, 23) + SourceIndex(0)
-9 >Emitted(24, 53) Source(18, 24) + SourceIndex(0)
+1->Emitted(28, 9) Source(18, 5) + SourceIndex(0)
+2 >Emitted(28, 20) Source(18, 10) + SourceIndex(0)
+3 >Emitted(28, 23) Source(18, 13) + SourceIndex(0)
+4 >Emitted(28, 37) Source(18, 19) + SourceIndex(0)
+5 >Emitted(28, 44) Source(18, 19) + SourceIndex(0)
+6 >Emitted(28, 49) Source(18, 23) + SourceIndex(0)
+7 >Emitted(28, 51) Source(18, 19) + SourceIndex(0)
+8 >Emitted(28, 52) Source(18, 23) + SourceIndex(0)
+9 >Emitted(28, 53) Source(18, 24) + SourceIndex(0)
 ---
 >>>        if (Math.random() < 0.5) {
 1 >^^^^^^^^
@@ -362,19 +366,19 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 11>                               )
 12>                                 
 13>                                 {
-1 >Emitted(25, 9) Source(23, 9) + SourceIndex(0)
-2 >Emitted(25, 11) Source(23, 11) + SourceIndex(0)
-3 >Emitted(25, 12) Source(23, 12) + SourceIndex(0)
-4 >Emitted(25, 13) Source(23, 13) + SourceIndex(0)
-5 >Emitted(25, 17) Source(23, 17) + SourceIndex(0)
-6 >Emitted(25, 18) Source(23, 18) + SourceIndex(0)
-7 >Emitted(25, 24) Source(23, 24) + SourceIndex(0)
-8 >Emitted(25, 26) Source(23, 26) + SourceIndex(0)
-9 >Emitted(25, 29) Source(23, 29) + SourceIndex(0)
-10>Emitted(25, 32) Source(23, 32) + SourceIndex(0)
-11>Emitted(25, 33) Source(23, 33) + SourceIndex(0)
-12>Emitted(25, 34) Source(23, 34) + SourceIndex(0)
-13>Emitted(25, 35) Source(23, 35) + SourceIndex(0)
+1 >Emitted(29, 9) Source(23, 9) + SourceIndex(0)
+2 >Emitted(29, 11) Source(23, 11) + SourceIndex(0)
+3 >Emitted(29, 12) Source(23, 12) + SourceIndex(0)
+4 >Emitted(29, 13) Source(23, 13) + SourceIndex(0)
+5 >Emitted(29, 17) Source(23, 17) + SourceIndex(0)
+6 >Emitted(29, 18) Source(23, 18) + SourceIndex(0)
+7 >Emitted(29, 24) Source(23, 24) + SourceIndex(0)
+8 >Emitted(29, 26) Source(23, 26) + SourceIndex(0)
+9 >Emitted(29, 29) Source(23, 29) + SourceIndex(0)
+10>Emitted(29, 32) Source(23, 32) + SourceIndex(0)
+11>Emitted(29, 33) Source(23, 33) + SourceIndex(0)
+12>Emitted(29, 34) Source(23, 34) + SourceIndex(0)
+13>Emitted(29, 35) Source(23, 35) + SourceIndex(0)
 ---
 >>>            "You win!";
 1 >^^^^^^^^^^^^
@@ -384,9 +388,9 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >            
 2 >            "You win!"
 3 >                      
-1 >Emitted(26, 13) Source(24, 13) + SourceIndex(0)
-2 >Emitted(26, 23) Source(24, 23) + SourceIndex(0)
-3 >Emitted(26, 24) Source(24, 23) + SourceIndex(0)
+1 >Emitted(30, 13) Source(24, 13) + SourceIndex(0)
+2 >Emitted(30, 23) Source(24, 23) + SourceIndex(0)
+3 >Emitted(30, 24) Source(24, 23) + SourceIndex(0)
 ---
 >>>            return {
 1 >^^^^^^^^^^^^
@@ -397,9 +401,9 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >            
 2 >            return
 3 >                   
-1 >Emitted(27, 13) Source(25, 13) + SourceIndex(0)
-2 >Emitted(27, 19) Source(25, 19) + SourceIndex(0)
-3 >Emitted(27, 20) Source(25, 20) + SourceIndex(0)
+1 >Emitted(31, 13) Source(25, 13) + SourceIndex(0)
+2 >Emitted(31, 19) Source(25, 19) + SourceIndex(0)
+3 >Emitted(31, 20) Source(25, 20) + SourceIndex(0)
 ---
 >>>                cProp: 1,
 1->^^^^^^^^^^^^^^^^
@@ -412,10 +416,10 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 2 >                cProp
 3 >                     : 
 4 >                       1
-1->Emitted(28, 17) Source(26, 17) + SourceIndex(0)
-2 >Emitted(28, 22) Source(26, 22) + SourceIndex(0)
-3 >Emitted(28, 24) Source(26, 24) + SourceIndex(0)
-4 >Emitted(28, 25) Source(26, 25) + SourceIndex(0)
+1->Emitted(32, 17) Source(26, 17) + SourceIndex(0)
+2 >Emitted(32, 22) Source(26, 22) + SourceIndex(0)
+3 >Emitted(32, 24) Source(26, 24) + SourceIndex(0)
+4 >Emitted(32, 25) Source(26, 25) + SourceIndex(0)
 ---
 >>>                dProp: function () { return _this; },
 1->^^^^^^^^^^^^^^^^
@@ -436,14 +440,14 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 6 >                                            this
 7 >                                                 
 8 >                                                   this
-1->Emitted(29, 17) Source(27, 17) + SourceIndex(0)
-2 >Emitted(29, 22) Source(27, 22) + SourceIndex(0)
-3 >Emitted(29, 24) Source(27, 24) + SourceIndex(0)
-4 >Emitted(29, 38) Source(27, 30) + SourceIndex(0)
-5 >Emitted(29, 45) Source(27, 30) + SourceIndex(0)
-6 >Emitted(29, 50) Source(27, 34) + SourceIndex(0)
-7 >Emitted(29, 52) Source(27, 30) + SourceIndex(0)
-8 >Emitted(29, 53) Source(27, 34) + SourceIndex(0)
+1->Emitted(33, 17) Source(27, 17) + SourceIndex(0)
+2 >Emitted(33, 22) Source(27, 22) + SourceIndex(0)
+3 >Emitted(33, 24) Source(27, 24) + SourceIndex(0)
+4 >Emitted(33, 38) Source(27, 30) + SourceIndex(0)
+5 >Emitted(33, 45) Source(27, 30) + SourceIndex(0)
+6 >Emitted(33, 50) Source(27, 34) + SourceIndex(0)
+7 >Emitted(33, 52) Source(27, 30) + SourceIndex(0)
+8 >Emitted(33, 53) Source(27, 34) + SourceIndex(0)
 ---
 >>>                foo: function () { return "You win!!!!!"; }
 1->^^^^^^^^^^^^^^^^
@@ -465,15 +469,15 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 7 >                                                        
 8 >                                                          
 9 >                                                          }
-1->Emitted(30, 17) Source(28, 17) + SourceIndex(0)
-2 >Emitted(30, 20) Source(28, 20) + SourceIndex(0)
-3 >Emitted(30, 36) Source(28, 25) + SourceIndex(0)
-4 >Emitted(30, 42) Source(28, 31) + SourceIndex(0)
-5 >Emitted(30, 43) Source(28, 32) + SourceIndex(0)
-6 >Emitted(30, 57) Source(28, 46) + SourceIndex(0)
-7 >Emitted(30, 58) Source(28, 46) + SourceIndex(0)
-8 >Emitted(30, 59) Source(28, 47) + SourceIndex(0)
-9 >Emitted(30, 60) Source(28, 48) + SourceIndex(0)
+1->Emitted(34, 17) Source(28, 17) + SourceIndex(0)
+2 >Emitted(34, 20) Source(28, 20) + SourceIndex(0)
+3 >Emitted(34, 36) Source(28, 25) + SourceIndex(0)
+4 >Emitted(34, 42) Source(28, 31) + SourceIndex(0)
+5 >Emitted(34, 43) Source(28, 32) + SourceIndex(0)
+6 >Emitted(34, 57) Source(28, 46) + SourceIndex(0)
+7 >Emitted(34, 58) Source(28, 46) + SourceIndex(0)
+8 >Emitted(34, 59) Source(28, 47) + SourceIndex(0)
+9 >Emitted(34, 60) Source(28, 48) + SourceIndex(0)
 ---
 >>>            };
 1 >^^^^^^^^^^^^^
@@ -481,8 +485,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1 >
   >            }
 2 >             ;
-1 >Emitted(31, 14) Source(29, 14) + SourceIndex(0)
-2 >Emitted(31, 15) Source(29, 15) + SourceIndex(0)
+1 >Emitted(35, 14) Source(29, 14) + SourceIndex(0)
+2 >Emitted(35, 15) Source(29, 15) + SourceIndex(0)
 ---
 >>>        }
 1 >^^^^^^^^
@@ -491,8 +495,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1 >
   >        
 2 >        }
-1 >Emitted(32, 9) Source(30, 9) + SourceIndex(0)
-2 >Emitted(32, 10) Source(30, 10) + SourceIndex(0)
+1 >Emitted(36, 9) Source(30, 9) + SourceIndex(0)
+2 >Emitted(36, 10) Source(30, 10) + SourceIndex(0)
 ---
 >>>        else
 1->^^^^^^^^
@@ -501,8 +505,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1->
   >        
 2 >        else
-1->Emitted(33, 9) Source(31, 9) + SourceIndex(0)
-2 >Emitted(33, 13) Source(31, 13) + SourceIndex(0)
+1->Emitted(37, 9) Source(31, 9) + SourceIndex(0)
+2 >Emitted(37, 13) Source(31, 13) + SourceIndex(0)
 ---
 >>>            return null;
 1->^^^^^^^^^^^^
@@ -516,11 +520,11 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 3 >                   
 4 >                   null
 5 >                       ;
-1->Emitted(34, 13) Source(32, 13) + SourceIndex(0)
-2 >Emitted(34, 19) Source(32, 19) + SourceIndex(0)
-3 >Emitted(34, 20) Source(32, 20) + SourceIndex(0)
-4 >Emitted(34, 24) Source(32, 24) + SourceIndex(0)
-5 >Emitted(34, 25) Source(32, 25) + SourceIndex(0)
+1->Emitted(38, 13) Source(32, 13) + SourceIndex(0)
+2 >Emitted(38, 19) Source(32, 19) + SourceIndex(0)
+3 >Emitted(38, 20) Source(32, 20) + SourceIndex(0)
+4 >Emitted(38, 24) Source(32, 24) + SourceIndex(0)
+5 >Emitted(38, 25) Source(32, 25) + SourceIndex(0)
 ---
 >>>    }
 1 >^^^^
@@ -529,8 +533,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1 >
   >    
 2 >    }
-1 >Emitted(35, 5) Source(33, 5) + SourceIndex(0)
-2 >Emitted(35, 6) Source(33, 6) + SourceIndex(0)
+1 >Emitted(39, 5) Source(33, 5) + SourceIndex(0)
+2 >Emitted(39, 6) Source(33, 6) + SourceIndex(0)
 ---
 >>>    return D;
 1->^^^^
@@ -538,8 +542,8 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
 1->
   >
 2 >    }
-1->Emitted(36, 5) Source(34, 1) + SourceIndex(0)
-2 >Emitted(36, 13) Source(34, 2) + SourceIndex(0)
+1->Emitted(40, 5) Source(34, 1) + SourceIndex(0)
+2 >Emitted(40, 13) Source(34, 2) + SourceIndex(0)
 ---
 >>>}(C));
 1 >
@@ -572,11 +576,11 @@ sourceFile:derivedClassConstructorWithExplicitReturns01.ts
   >               return null;
   >       }
   >   }
-1 >Emitted(37, 1) Source(34, 1) + SourceIndex(0)
-2 >Emitted(37, 2) Source(34, 2) + SourceIndex(0)
-3 >Emitted(37, 2) Source(17, 1) + SourceIndex(0)
-4 >Emitted(37, 3) Source(17, 17) + SourceIndex(0)
-5 >Emitted(37, 4) Source(17, 18) + SourceIndex(0)
-6 >Emitted(37, 7) Source(34, 2) + SourceIndex(0)
+1 >Emitted(41, 1) Source(34, 1) + SourceIndex(0)
+2 >Emitted(41, 2) Source(34, 2) + SourceIndex(0)
+3 >Emitted(41, 2) Source(17, 1) + SourceIndex(0)
+4 >Emitted(41, 3) Source(17, 17) + SourceIndex(0)
+5 >Emitted(41, 4) Source(17, 18) + SourceIndex(0)
+6 >Emitted(41, 7) Source(34, 2) + SourceIndex(0)
 ---
 >>>//# sourceMappingURL=derivedClassConstructorWithExplicitReturns01.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/derivedClassConstructorWithoutSuperCall.js b/tests/baselines/reference/derivedClassConstructorWithoutSuperCall.js
index 55ceea201ed..31c8c3f722c 100644
--- a/tests/baselines/reference/derivedClassConstructorWithoutSuperCall.js
+++ b/tests/baselines/reference/derivedClassConstructorWithoutSuperCall.js
@@ -35,7 +35,11 @@ class Derived4<T> extends Base2<T> {
 //// [derivedClassConstructorWithoutSuperCall.js]
 // derived class constructors must contain a super call
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassFunctionOverridesBaseClassAccessor.js b/tests/baselines/reference/derivedClassFunctionOverridesBaseClassAccessor.js
index fe6be20e2ac..b948302a2d5 100644
--- a/tests/baselines/reference/derivedClassFunctionOverridesBaseClassAccessor.js
+++ b/tests/baselines/reference/derivedClassFunctionOverridesBaseClassAccessor.js
@@ -16,7 +16,11 @@ class Derived extends Base {
 
 //// [derivedClassFunctionOverridesBaseClassAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassIncludesInheritedMembers.js b/tests/baselines/reference/derivedClassIncludesInheritedMembers.js
index 8b6f6fe34cb..cf5454d704f 100644
--- a/tests/baselines/reference/derivedClassIncludesInheritedMembers.js
+++ b/tests/baselines/reference/derivedClassIncludesInheritedMembers.js
@@ -42,7 +42,11 @@ var r8 = d2[1];
 
 //// [derivedClassIncludesInheritedMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesIndexersWithAssignmentCompatibility.js b/tests/baselines/reference/derivedClassOverridesIndexersWithAssignmentCompatibility.js
index 80fd6fd251c..0d483a3eff6 100644
--- a/tests/baselines/reference/derivedClassOverridesIndexersWithAssignmentCompatibility.js
+++ b/tests/baselines/reference/derivedClassOverridesIndexersWithAssignmentCompatibility.js
@@ -19,7 +19,11 @@ class Derived2 extends Base2 {
 
 //// [derivedClassOverridesIndexersWithAssignmentCompatibility.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesPrivateFunction1.js b/tests/baselines/reference/derivedClassOverridesPrivateFunction1.js
index c5d48de031e..8306e702cb1 100644
--- a/tests/baselines/reference/derivedClassOverridesPrivateFunction1.js
+++ b/tests/baselines/reference/derivedClassOverridesPrivateFunction1.js
@@ -17,7 +17,11 @@ new DerivedClass();
 
 //// [derivedClassOverridesPrivateFunction1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesPrivates.js b/tests/baselines/reference/derivedClassOverridesPrivates.js
index fa4b88bdc56..c32560eca59 100644
--- a/tests/baselines/reference/derivedClassOverridesPrivates.js
+++ b/tests/baselines/reference/derivedClassOverridesPrivates.js
@@ -17,7 +17,11 @@ class Derived2 extends Base2 {
 
 //// [derivedClassOverridesPrivates.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesProtectedMembers.js b/tests/baselines/reference/derivedClassOverridesProtectedMembers.js
index b4fb59ffd2c..03addf8ace5 100644
--- a/tests/baselines/reference/derivedClassOverridesProtectedMembers.js
+++ b/tests/baselines/reference/derivedClassOverridesProtectedMembers.js
@@ -38,7 +38,11 @@ class Derived extends Base {
 
 //// [derivedClassOverridesProtectedMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesProtectedMembers2.js b/tests/baselines/reference/derivedClassOverridesProtectedMembers2.js
index 13f2cfc4698..0cfe6f3dd9d 100644
--- a/tests/baselines/reference/derivedClassOverridesProtectedMembers2.js
+++ b/tests/baselines/reference/derivedClassOverridesProtectedMembers2.js
@@ -65,7 +65,11 @@ var r8 = d2[1];
 
 //// [derivedClassOverridesProtectedMembers2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesProtectedMembers3.js b/tests/baselines/reference/derivedClassOverridesProtectedMembers3.js
index 24602737e6b..d18fd9d1a30 100644
--- a/tests/baselines/reference/derivedClassOverridesProtectedMembers3.js
+++ b/tests/baselines/reference/derivedClassOverridesProtectedMembers3.js
@@ -73,7 +73,11 @@ class Derived10 extends Base {
 
 //// [derivedClassOverridesProtectedMembers3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesProtectedMembers4.js b/tests/baselines/reference/derivedClassOverridesProtectedMembers4.js
index add886d1985..2d89040ff13 100644
--- a/tests/baselines/reference/derivedClassOverridesProtectedMembers4.js
+++ b/tests/baselines/reference/derivedClassOverridesProtectedMembers4.js
@@ -16,7 +16,11 @@ class Derived2 extends Derived1 {
 
 //// [derivedClassOverridesProtectedMembers4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesPublicMembers.js b/tests/baselines/reference/derivedClassOverridesPublicMembers.js
index d8fa9e82683..2ef057082bd 100644
--- a/tests/baselines/reference/derivedClassOverridesPublicMembers.js
+++ b/tests/baselines/reference/derivedClassOverridesPublicMembers.js
@@ -64,7 +64,11 @@ var r8 = d2[1];
 
 //// [derivedClassOverridesPublicMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassOverridesWithoutSubtype.js b/tests/baselines/reference/derivedClassOverridesWithoutSubtype.js
index bcd4e505721..4a1f7c0cbeb 100644
--- a/tests/baselines/reference/derivedClassOverridesWithoutSubtype.js
+++ b/tests/baselines/reference/derivedClassOverridesWithoutSubtype.js
@@ -25,7 +25,11 @@ class Derived2 extends Base2 {
 
 //// [derivedClassOverridesWithoutSubtype.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassParameterProperties.js b/tests/baselines/reference/derivedClassParameterProperties.js
index cb08d4d8545..cdf1ab4cbbd 100644
--- a/tests/baselines/reference/derivedClassParameterProperties.js
+++ b/tests/baselines/reference/derivedClassParameterProperties.js
@@ -97,7 +97,11 @@ class Derived10<T> extends Base2<T> {
 //// [derivedClassParameterProperties.js]
 // ordering of super calls in derived constructors matters depending on other class contents
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassSuperCallsInNonConstructorMembers.js b/tests/baselines/reference/derivedClassSuperCallsInNonConstructorMembers.js
index cf7845a4d9a..c7a90e31dfe 100644
--- a/tests/baselines/reference/derivedClassSuperCallsInNonConstructorMembers.js
+++ b/tests/baselines/reference/derivedClassSuperCallsInNonConstructorMembers.js
@@ -34,7 +34,11 @@ class Derived extends Base {
 //// [derivedClassSuperCallsInNonConstructorMembers.js]
 // error to use super calls outside a constructor
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassSuperCallsWithThisArg.js b/tests/baselines/reference/derivedClassSuperCallsWithThisArg.js
index 59a4ff7e1d1..3d3aacdf55b 100644
--- a/tests/baselines/reference/derivedClassSuperCallsWithThisArg.js
+++ b/tests/baselines/reference/derivedClassSuperCallsWithThisArg.js
@@ -30,7 +30,11 @@ class Derived4 extends Base {
 
 //// [derivedClassSuperCallsWithThisArg.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassTransitivity.js b/tests/baselines/reference/derivedClassTransitivity.js
index 6a6b713f250..c5ea3722feb 100644
--- a/tests/baselines/reference/derivedClassTransitivity.js
+++ b/tests/baselines/reference/derivedClassTransitivity.js
@@ -23,7 +23,11 @@ var r2 = e.foo('');
 //// [derivedClassTransitivity.js]
 // subclassing is not transitive when you can remove required parameters and add optional parameters
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassTransitivity2.js b/tests/baselines/reference/derivedClassTransitivity2.js
index 2d05dd09cee..bf9f1dbb574 100644
--- a/tests/baselines/reference/derivedClassTransitivity2.js
+++ b/tests/baselines/reference/derivedClassTransitivity2.js
@@ -23,7 +23,11 @@ var r2 = e.foo(1, '');
 //// [derivedClassTransitivity2.js]
 // subclassing is not transitive when you can remove required parameters and add optional parameters
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassTransitivity3.js b/tests/baselines/reference/derivedClassTransitivity3.js
index 6c02e2055d9..d149d9f5aa9 100644
--- a/tests/baselines/reference/derivedClassTransitivity3.js
+++ b/tests/baselines/reference/derivedClassTransitivity3.js
@@ -23,7 +23,11 @@ var r2 = e.foo('', 1);
 //// [derivedClassTransitivity3.js]
 // subclassing is not transitive when you can remove required parameters and add optional parameters
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassTransitivity4.js b/tests/baselines/reference/derivedClassTransitivity4.js
index 7d375e8e94e..2d48cf28728 100644
--- a/tests/baselines/reference/derivedClassTransitivity4.js
+++ b/tests/baselines/reference/derivedClassTransitivity4.js
@@ -23,7 +23,11 @@ var r2 = e.foo('');
 //// [derivedClassTransitivity4.js]
 // subclassing is not transitive when you can remove required parameters and add optional parameters on protected members
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithAny.js b/tests/baselines/reference/derivedClassWithAny.js
index 51b4e5739f6..b376364e542 100644
--- a/tests/baselines/reference/derivedClassWithAny.js
+++ b/tests/baselines/reference/derivedClassWithAny.js
@@ -61,7 +61,11 @@ var r = c.foo(); // e.foo would return string
 
 //// [derivedClassWithAny.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingProtectedInstance.js b/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingProtectedInstance.js
index 8a86f4ab4a9..e5fe6eb2560 100644
--- a/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingProtectedInstance.js
+++ b/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingProtectedInstance.js
@@ -24,7 +24,11 @@ class Derived extends Base {
 
 //// [derivedClassWithPrivateInstanceShadowingProtectedInstance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingPublicInstance.js b/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingPublicInstance.js
index fab643265cb..5ac36e99b57 100644
--- a/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingPublicInstance.js
+++ b/tests/baselines/reference/derivedClassWithPrivateInstanceShadowingPublicInstance.js
@@ -34,7 +34,11 @@ Derived.a = 2; // error
 
 //// [derivedClassWithPrivateInstanceShadowingPublicInstance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithPrivateStaticShadowingProtectedStatic.js b/tests/baselines/reference/derivedClassWithPrivateStaticShadowingProtectedStatic.js
index 322514e1c82..9994c1bfb05 100644
--- a/tests/baselines/reference/derivedClassWithPrivateStaticShadowingProtectedStatic.js
+++ b/tests/baselines/reference/derivedClassWithPrivateStaticShadowingProtectedStatic.js
@@ -23,7 +23,11 @@ class Derived extends Base {
 
 //// [derivedClassWithPrivateStaticShadowingProtectedStatic.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithPrivateStaticShadowingPublicStatic.js b/tests/baselines/reference/derivedClassWithPrivateStaticShadowingPublicStatic.js
index 8c01a45e1ae..4183017f378 100644
--- a/tests/baselines/reference/derivedClassWithPrivateStaticShadowingPublicStatic.js
+++ b/tests/baselines/reference/derivedClassWithPrivateStaticShadowingPublicStatic.js
@@ -35,7 +35,11 @@ Derived.a = 2; // error
 
 //// [derivedClassWithPrivateStaticShadowingPublicStatic.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithoutExplicitConstructor.js b/tests/baselines/reference/derivedClassWithoutExplicitConstructor.js
index 462819c551d..d21cb14bcc4 100644
--- a/tests/baselines/reference/derivedClassWithoutExplicitConstructor.js
+++ b/tests/baselines/reference/derivedClassWithoutExplicitConstructor.js
@@ -27,7 +27,11 @@ var d2 = new D(new Date()); // ok
 
 //// [derivedClassWithoutExplicitConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithoutExplicitConstructor2.js b/tests/baselines/reference/derivedClassWithoutExplicitConstructor2.js
index 6e7c75ef37d..0acf65cd177 100644
--- a/tests/baselines/reference/derivedClassWithoutExplicitConstructor2.js
+++ b/tests/baselines/reference/derivedClassWithoutExplicitConstructor2.js
@@ -35,7 +35,11 @@ var d4 = new D(new Date(), new Date(), new Date());
 
 //// [derivedClassWithoutExplicitConstructor2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClassWithoutExplicitConstructor3.js b/tests/baselines/reference/derivedClassWithoutExplicitConstructor3.js
index 4d4527c172e..696ebcc1f9e 100644
--- a/tests/baselines/reference/derivedClassWithoutExplicitConstructor3.js
+++ b/tests/baselines/reference/derivedClassWithoutExplicitConstructor3.js
@@ -49,7 +49,11 @@ var d3 = new D2(new Date(), new Date()); // ok
 //// [derivedClassWithoutExplicitConstructor3.js]
 // automatic constructors with a class hieararchy of depth > 2
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedClasses.js b/tests/baselines/reference/derivedClasses.js
index 00bdfcfde4e..36f1dcc799b 100644
--- a/tests/baselines/reference/derivedClasses.js
+++ b/tests/baselines/reference/derivedClasses.js
@@ -32,7 +32,11 @@ b.hue();
 
 //// [derivedClasses.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedGenericClassWithAny.js b/tests/baselines/reference/derivedGenericClassWithAny.js
index 410027ce76d..afba93ccac6 100644
--- a/tests/baselines/reference/derivedGenericClassWithAny.js
+++ b/tests/baselines/reference/derivedGenericClassWithAny.js
@@ -44,7 +44,11 @@ var r = c.foo(); // e.foo would return string
 
 //// [derivedGenericClassWithAny.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedTypeAccessesHiddenBaseCallViaSuperPropertyAccess.js b/tests/baselines/reference/derivedTypeAccessesHiddenBaseCallViaSuperPropertyAccess.js
index 367b0d895cf..c33bd3713fc 100644
--- a/tests/baselines/reference/derivedTypeAccessesHiddenBaseCallViaSuperPropertyAccess.js
+++ b/tests/baselines/reference/derivedTypeAccessesHiddenBaseCallViaSuperPropertyAccess.js
@@ -19,7 +19,11 @@ class Derived extends Base {
 
 //// [derivedTypeAccessesHiddenBaseCallViaSuperPropertyAccess.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/derivedTypeDoesNotRequireExtendsClause.js b/tests/baselines/reference/derivedTypeDoesNotRequireExtendsClause.js
index c890a28b110..3e28aece101 100644
--- a/tests/baselines/reference/derivedTypeDoesNotRequireExtendsClause.js
+++ b/tests/baselines/reference/derivedTypeDoesNotRequireExtendsClause.js
@@ -22,7 +22,11 @@ var r: Base[] = [d1, d2];
 
 //// [derivedTypeDoesNotRequireExtendsClause.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/destructuringParameterDeclaration5.js b/tests/baselines/reference/destructuringParameterDeclaration5.js
index d7b75ede23d..0c27e9b7f85 100644
--- a/tests/baselines/reference/destructuringParameterDeclaration5.js
+++ b/tests/baselines/reference/destructuringParameterDeclaration5.js
@@ -53,7 +53,11 @@ d3({ y: "world" });
 //// [destructuringParameterDeclaration5.js]
 // Parameter Declaration with generic
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/emitSuperCallBeforeEmitParameterPropertyDeclaration1.js b/tests/baselines/reference/emitSuperCallBeforeEmitParameterPropertyDeclaration1.js
index fbc08b66624..80613c66be8 100644
--- a/tests/baselines/reference/emitSuperCallBeforeEmitParameterPropertyDeclaration1.js
+++ b/tests/baselines/reference/emitSuperCallBeforeEmitParameterPropertyDeclaration1.js
@@ -15,7 +15,11 @@ class B extends A {
 
 //// [emitSuperCallBeforeEmitParameterPropertyDeclaration1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclaration1.js b/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclaration1.js
index 1328ece2af0..c0478a993c4 100644
--- a/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclaration1.js
+++ b/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclaration1.js
@@ -17,7 +17,11 @@ class B extends A {
 
 //// [emitSuperCallBeforeEmitPropertyDeclaration1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclarationAndParameterPropertyDeclaration1.js b/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclarationAndParameterPropertyDeclaration1.js
index a9883b26e30..5d63f4f32af 100644
--- a/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclarationAndParameterPropertyDeclaration1.js
+++ b/tests/baselines/reference/emitSuperCallBeforeEmitPropertyDeclarationAndParameterPropertyDeclaration1.js
@@ -15,7 +15,11 @@ class B extends A {
 
 //// [emitSuperCallBeforeEmitPropertyDeclarationAndParameterPropertyDeclaration1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/emitThisInSuperMethodCall.js b/tests/baselines/reference/emitThisInSuperMethodCall.js
index 1e23553a2d9..22d641e3414 100644
--- a/tests/baselines/reference/emitThisInSuperMethodCall.js
+++ b/tests/baselines/reference/emitThisInSuperMethodCall.js
@@ -29,7 +29,11 @@ class RegisteredUser extends User {
 
 //// [emitThisInSuperMethodCall.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/emptyModuleName.js b/tests/baselines/reference/emptyModuleName.js
index 404abf6a42c..f6f4ea759a6 100644
--- a/tests/baselines/reference/emptyModuleName.js
+++ b/tests/baselines/reference/emptyModuleName.js
@@ -6,7 +6,11 @@ class B extends A {
 //// [emptyModuleName.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/errorForwardReferenceForwadingConstructor.js b/tests/baselines/reference/errorForwardReferenceForwadingConstructor.js
index 2bfac7ec0f0..3320b144f11 100644
--- a/tests/baselines/reference/errorForwardReferenceForwadingConstructor.js
+++ b/tests/baselines/reference/errorForwardReferenceForwadingConstructor.js
@@ -13,7 +13,11 @@ class derived extends base { }
 //// [errorForwardReferenceForwadingConstructor.js]
 // Error forward referencing derived class with forwarding constructor
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/errorSuperCalls.js b/tests/baselines/reference/errorSuperCalls.js
index 4e228777567..69691a62bb7 100644
--- a/tests/baselines/reference/errorSuperCalls.js
+++ b/tests/baselines/reference/errorSuperCalls.js
@@ -76,7 +76,11 @@ class OtherDerived extends OtherBase {
 
 //// [errorSuperCalls.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/errorSuperPropertyAccess.js b/tests/baselines/reference/errorSuperPropertyAccess.js
index 62bb9919171..ed9ac2d8dd5 100644
--- a/tests/baselines/reference/errorSuperPropertyAccess.js
+++ b/tests/baselines/reference/errorSuperPropertyAccess.js
@@ -130,7 +130,11 @@ var obj = { n: super.wat, p: super.foo() };
 
 //// [errorSuperPropertyAccess.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/errorsInGenericTypeReference.js b/tests/baselines/reference/errorsInGenericTypeReference.js
index bb80f73f216..e63005bfe1a 100644
--- a/tests/baselines/reference/errorsInGenericTypeReference.js
+++ b/tests/baselines/reference/errorsInGenericTypeReference.js
@@ -74,7 +74,11 @@ interface testInterface2 {
 
 //// [errorsInGenericTypeReference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/es6ClassSuperCodegenBug.js b/tests/baselines/reference/es6ClassSuperCodegenBug.js
index fc6ad83738d..af87c3db821 100644
--- a/tests/baselines/reference/es6ClassSuperCodegenBug.js
+++ b/tests/baselines/reference/es6ClassSuperCodegenBug.js
@@ -16,7 +16,11 @@ class B extends A {
 
 //// [es6ClassSuperCodegenBug.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/es6ClassTest.js b/tests/baselines/reference/es6ClassTest.js
index 8fa5be0ba3e..a20d939a794 100644
--- a/tests/baselines/reference/es6ClassTest.js
+++ b/tests/baselines/reference/es6ClassTest.js
@@ -86,7 +86,11 @@ declare module AmbientMod {
 
 //// [es6ClassTest.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/es6ClassTest2.js b/tests/baselines/reference/es6ClassTest2.js
index 7004c7056f2..11d494c6291 100644
--- a/tests/baselines/reference/es6ClassTest2.js
+++ b/tests/baselines/reference/es6ClassTest2.js
@@ -160,7 +160,11 @@ var ccwc = new ChildClassWithoutConstructor(1, "s");
 
 //// [es6ClassTest2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/es6ClassTest7.js b/tests/baselines/reference/es6ClassTest7.js
index 20d46e6b53c..9cd21f44685 100644
--- a/tests/baselines/reference/es6ClassTest7.js
+++ b/tests/baselines/reference/es6ClassTest7.js
@@ -10,7 +10,11 @@ class Bar extends M.Foo {
 
 //// [es6ClassTest7.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/exportAssignmentOfGenericType1.js b/tests/baselines/reference/exportAssignmentOfGenericType1.js
index 431da58c12e..e5d43bfaa9e 100644
--- a/tests/baselines/reference/exportAssignmentOfGenericType1.js
+++ b/tests/baselines/reference/exportAssignmentOfGenericType1.js
@@ -25,7 +25,11 @@ define(["require", "exports"], function (require, exports) {
 });
 //// [exportAssignmentOfGenericType1_1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/exportDeclarationInInternalModule.js b/tests/baselines/reference/exportDeclarationInInternalModule.js
index ddc2e15a5b2..934b3bb6ef0 100644
--- a/tests/baselines/reference/exportDeclarationInInternalModule.js
+++ b/tests/baselines/reference/exportDeclarationInInternalModule.js
@@ -20,7 +20,11 @@ var a: Bbb.SomeType;
 
 //// [exportDeclarationInInternalModule.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extBaseClass1.js b/tests/baselines/reference/extBaseClass1.js
index d8eb5e75f9f..4603ff26320 100644
--- a/tests/baselines/reference/extBaseClass1.js
+++ b/tests/baselines/reference/extBaseClass1.js
@@ -21,7 +21,11 @@ module N {
 
 //// [extBaseClass1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extBaseClass2.js b/tests/baselines/reference/extBaseClass2.js
index 474a91d2a72..285c96551b5 100644
--- a/tests/baselines/reference/extBaseClass2.js
+++ b/tests/baselines/reference/extBaseClass2.js
@@ -12,7 +12,11 @@ module M {
 
 //// [extBaseClass2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendAndImplementTheSameBaseType.js b/tests/baselines/reference/extendAndImplementTheSameBaseType.js
index 1342df1b992..b3150a12bde 100644
--- a/tests/baselines/reference/extendAndImplementTheSameBaseType.js
+++ b/tests/baselines/reference/extendAndImplementTheSameBaseType.js
@@ -15,7 +15,11 @@ d.foo;
 
 //// [extendAndImplementTheSameBaseType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendAndImplementTheSameBaseType2.js b/tests/baselines/reference/extendAndImplementTheSameBaseType2.js
index 38b76b19942..1ecd77668d3 100644
--- a/tests/baselines/reference/extendAndImplementTheSameBaseType2.js
+++ b/tests/baselines/reference/extendAndImplementTheSameBaseType2.js
@@ -18,7 +18,11 @@ var r4: number = d.bar();
 
 //// [extendAndImplementTheSameBaseType2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendBaseClassBeforeItsDeclared.js b/tests/baselines/reference/extendBaseClassBeforeItsDeclared.js
index 8cf51642831..73c19b72565 100644
--- a/tests/baselines/reference/extendBaseClassBeforeItsDeclared.js
+++ b/tests/baselines/reference/extendBaseClassBeforeItsDeclared.js
@@ -5,7 +5,11 @@ class base { constructor (public n: number) { } }
 
 //// [extendBaseClassBeforeItsDeclared.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendClassExpressionFromModule.js b/tests/baselines/reference/extendClassExpressionFromModule.js
index 27420b55d1c..bd3e01a7b29 100644
--- a/tests/baselines/reference/extendClassExpressionFromModule.js
+++ b/tests/baselines/reference/extendClassExpressionFromModule.js
@@ -22,7 +22,11 @@ module.exports = x;
 //// [foo2.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendConstructSignatureInInterface.js b/tests/baselines/reference/extendConstructSignatureInInterface.js
index db87c4c14fd..28c5108f238 100644
--- a/tests/baselines/reference/extendConstructSignatureInInterface.js
+++ b/tests/baselines/reference/extendConstructSignatureInInterface.js
@@ -12,7 +12,11 @@ var e: E = new E(1);
 
 //// [extendConstructSignatureInInterface.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendNonClassSymbol1.js b/tests/baselines/reference/extendNonClassSymbol1.js
index 00326e24103..8a6da5f4fa7 100644
--- a/tests/baselines/reference/extendNonClassSymbol1.js
+++ b/tests/baselines/reference/extendNonClassSymbol1.js
@@ -5,7 +5,11 @@ class C extends x { } // error, could not find symbol xs
 
 //// [extendNonClassSymbol1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendNonClassSymbol2.js b/tests/baselines/reference/extendNonClassSymbol2.js
index ce030629af5..60f7a46a14f 100644
--- a/tests/baselines/reference/extendNonClassSymbol2.js
+++ b/tests/baselines/reference/extendNonClassSymbol2.js
@@ -7,7 +7,11 @@ class C extends Foo {} // error, could not find symbol Foo
 
 //// [extendNonClassSymbol2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendPrivateConstructorClass.js b/tests/baselines/reference/extendPrivateConstructorClass.js
index 52b96e31611..983c7220397 100644
--- a/tests/baselines/reference/extendPrivateConstructorClass.js
+++ b/tests/baselines/reference/extendPrivateConstructorClass.js
@@ -11,7 +11,11 @@ class C extends abc.XYZ {
 
 //// [extendPrivateConstructorClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendingClassFromAliasAndUsageInIndexer.js b/tests/baselines/reference/extendingClassFromAliasAndUsageInIndexer.js
index 92c5dc69681..af5f78dfcec 100644
--- a/tests/baselines/reference/extendingClassFromAliasAndUsageInIndexer.js
+++ b/tests/baselines/reference/extendingClassFromAliasAndUsageInIndexer.js
@@ -43,7 +43,11 @@ exports.Model = Model;
 //// [extendingClassFromAliasAndUsageInIndexer_moduleA.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -59,7 +63,11 @@ exports.VisualizationModel = VisualizationModel;
 //// [extendingClassFromAliasAndUsageInIndexer_moduleB.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendsClauseAlreadySeen.js b/tests/baselines/reference/extendsClauseAlreadySeen.js
index 37cdd0eb9bc..06326b54282 100644
--- a/tests/baselines/reference/extendsClauseAlreadySeen.js
+++ b/tests/baselines/reference/extendsClauseAlreadySeen.js
@@ -8,7 +8,11 @@ class D extends C extends C {
 
 //// [extendsClauseAlreadySeen.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/extendsClauseAlreadySeen2.js b/tests/baselines/reference/extendsClauseAlreadySeen2.js
index bc4306884a3..71555248556 100644
--- a/tests/baselines/reference/extendsClauseAlreadySeen2.js
+++ b/tests/baselines/reference/extendsClauseAlreadySeen2.js
@@ -8,7 +8,11 @@ class D<T> extends C<number> extends C<string> {
 
 //// [extendsClauseAlreadySeen2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/fluentClasses.js b/tests/baselines/reference/fluentClasses.js
index ade60a06331..360c7775d35 100644
--- a/tests/baselines/reference/fluentClasses.js
+++ b/tests/baselines/reference/fluentClasses.js
@@ -20,7 +20,11 @@ var z = c.foo().bar().baz();  // Fluent pattern
 
 //// [fluentClasses.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/for-inStatements.js b/tests/baselines/reference/for-inStatements.js
index b34fd91192b..90ab9a3f96b 100644
--- a/tests/baselines/reference/for-inStatements.js
+++ b/tests/baselines/reference/for-inStatements.js
@@ -82,7 +82,11 @@ for (var x in Color.Blue) { }
 
 //// [for-inStatements.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/for-inStatementsInvalid.js b/tests/baselines/reference/for-inStatementsInvalid.js
index 3d39fb2903b..2ba55110f2e 100644
--- a/tests/baselines/reference/for-inStatementsInvalid.js
+++ b/tests/baselines/reference/for-inStatementsInvalid.js
@@ -65,7 +65,11 @@ for (var x in i[42]) { }
 
 //// [for-inStatementsInvalid.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/forStatementsMultipleInvalidDecl.js b/tests/baselines/reference/forStatementsMultipleInvalidDecl.js
index 8ca8c794cf5..31398cb2af9 100644
--- a/tests/baselines/reference/forStatementsMultipleInvalidDecl.js
+++ b/tests/baselines/reference/forStatementsMultipleInvalidDecl.js
@@ -56,7 +56,11 @@ for( var m = M.A;;){}
 
 //// [forStatementsMultipleInvalidDecl.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/functionImplementationErrors.js b/tests/baselines/reference/functionImplementationErrors.js
index 5c8defcf814..a91b1b78f07 100644
--- a/tests/baselines/reference/functionImplementationErrors.js
+++ b/tests/baselines/reference/functionImplementationErrors.js
@@ -76,7 +76,11 @@ var f13 = () => {
 
 //// [functionImplementationErrors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/functionImplementations.js b/tests/baselines/reference/functionImplementations.js
index e73e5095701..4854d715c32 100644
--- a/tests/baselines/reference/functionImplementations.js
+++ b/tests/baselines/reference/functionImplementations.js
@@ -159,7 +159,11 @@ var f12: (x: number) => any = x => { // should be (x: number) => Base | AnotherC
 
 //// [functionImplementations.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/functionSubtypingOfVarArgs.js b/tests/baselines/reference/functionSubtypingOfVarArgs.js
index 89e8b1e95ef..4cd1f1096f3 100644
--- a/tests/baselines/reference/functionSubtypingOfVarArgs.js
+++ b/tests/baselines/reference/functionSubtypingOfVarArgs.js
@@ -16,7 +16,11 @@ class StringEvent extends EventBase { // should work
 
 //// [functionSubtypingOfVarArgs.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/functionSubtypingOfVarArgs2.js b/tests/baselines/reference/functionSubtypingOfVarArgs2.js
index be9c293ae72..fc3562ca339 100644
--- a/tests/baselines/reference/functionSubtypingOfVarArgs2.js
+++ b/tests/baselines/reference/functionSubtypingOfVarArgs2.js
@@ -16,7 +16,11 @@ class StringEvent extends EventBase {
 
 //// [functionSubtypingOfVarArgs2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/generatedContextualTyping.js b/tests/baselines/reference/generatedContextualTyping.js
index 06abd1b9a8b..0cf8767aa58 100644
--- a/tests/baselines/reference/generatedContextualTyping.js
+++ b/tests/baselines/reference/generatedContextualTyping.js
@@ -357,7 +357,11 @@ var x356 = function(n: Genric<Base>) { }; x356({ func: n => { return [d1, d2]; }
 
 //// [generatedContextualTyping.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericBaseClassLiteralProperty.js b/tests/baselines/reference/genericBaseClassLiteralProperty.js
index b572cfae97d..753aa2f0733 100644
--- a/tests/baselines/reference/genericBaseClassLiteralProperty.js
+++ b/tests/baselines/reference/genericBaseClassLiteralProperty.js
@@ -14,7 +14,11 @@ class SubClass extends BaseClass<number> {
 
 //// [genericBaseClassLiteralProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericBaseClassLiteralProperty2.js b/tests/baselines/reference/genericBaseClassLiteralProperty2.js
index 9e99dee2b4c..131fc2d36ab 100644
--- a/tests/baselines/reference/genericBaseClassLiteralProperty2.js
+++ b/tests/baselines/reference/genericBaseClassLiteralProperty2.js
@@ -17,7 +17,11 @@ class DataView2 extends BaseCollection2<CollectionItem2> {
 
 //// [genericBaseClassLiteralProperty2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference.js b/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference.js
index 68a3e77f9ae..055ef9d2f86 100644
--- a/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference.js
+++ b/tests/baselines/reference/genericCallWithConstraintsTypeArgumentInference.js
@@ -110,7 +110,11 @@ var r11 = i.foo8(); // Base
 //// [genericCallWithConstraintsTypeArgumentInference.js]
 // Basic type inference with generic calls and constraints, no errors expected
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericCallWithObjectTypeArgs2.js b/tests/baselines/reference/genericCallWithObjectTypeArgs2.js
index 0b643db14cb..e4399d19037 100644
--- a/tests/baselines/reference/genericCallWithObjectTypeArgs2.js
+++ b/tests/baselines/reference/genericCallWithObjectTypeArgs2.js
@@ -34,7 +34,11 @@ var r4 = f2(i); // Base => Derived
 
 //// [genericCallWithObjectTypeArgs2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints2.js b/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints2.js
index 98448645d15..f86cc2da293 100644
--- a/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints2.js
+++ b/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints2.js
@@ -42,7 +42,11 @@ var r7 = f3(null, x => x); // any
 // Generic call with constraints infering type parameter from object member properties
 // No errors expected
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints3.js b/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints3.js
index 71bf682b0dc..01a11c7f90b 100644
--- a/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints3.js
+++ b/tests/baselines/reference/genericCallWithObjectTypeArgsAndConstraints3.js
@@ -40,7 +40,11 @@ var r6 = f3(x => x, null);
 //// [genericCallWithObjectTypeArgsAndConstraints3.js]
 // Generic call with constraints infering type parameter from object member properties
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericCallbacksAndClassHierarchy.js b/tests/baselines/reference/genericCallbacksAndClassHierarchy.js
index 67d0df1bc22..d4303fa2037 100644
--- a/tests/baselines/reference/genericCallbacksAndClassHierarchy.js
+++ b/tests/baselines/reference/genericCallbacksAndClassHierarchy.js
@@ -25,7 +25,11 @@ module M {
 
 //// [genericCallbacksAndClassHierarchy.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericClassExpressionInFunction.js b/tests/baselines/reference/genericClassExpressionInFunction.js
index 3db4d9693af..ab826e2916d 100644
--- a/tests/baselines/reference/genericClassExpressionInFunction.js
+++ b/tests/baselines/reference/genericClassExpressionInFunction.js
@@ -33,7 +33,11 @@ s.genericVar = 12;
 
 //// [genericClassExpressionInFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericClassInheritsConstructorFromNonGenericClass.js b/tests/baselines/reference/genericClassInheritsConstructorFromNonGenericClass.js
index 307c891f928..dbd654576ec 100644
--- a/tests/baselines/reference/genericClassInheritsConstructorFromNonGenericClass.js
+++ b/tests/baselines/reference/genericClassInheritsConstructorFromNonGenericClass.js
@@ -7,7 +7,11 @@ class C {
 
 //// [genericClassInheritsConstructorFromNonGenericClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericClassPropertyInheritanceSpecialization.js b/tests/baselines/reference/genericClassPropertyInheritanceSpecialization.js
index 147bbd8fb87..fa64843f29f 100644
--- a/tests/baselines/reference/genericClassPropertyInheritanceSpecialization.js
+++ b/tests/baselines/reference/genericClassPropertyInheritanceSpecialization.js
@@ -77,7 +77,11 @@ class ViewModel<TValue> implements Contract<TValue> {
 
 //// [genericClassPropertyInheritanceSpecialization.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericClassStaticMethod.js b/tests/baselines/reference/genericClassStaticMethod.js
index 257e7dbce97..8345b3d93a7 100644
--- a/tests/baselines/reference/genericClassStaticMethod.js
+++ b/tests/baselines/reference/genericClassStaticMethod.js
@@ -12,7 +12,11 @@ class Bar<T> extends Foo<T> {
 
 //// [genericClassStaticMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericClasses3.js b/tests/baselines/reference/genericClasses3.js
index fbc62b23aab..2f8d09eae03 100644
--- a/tests/baselines/reference/genericClasses3.js
+++ b/tests/baselines/reference/genericClasses3.js
@@ -19,7 +19,11 @@ var z = v2.b;
 
 //// [genericClasses3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes.js b/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes.js
index 4043924bf54..73fed8b3ea2 100644
--- a/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes.js
+++ b/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes.js
@@ -28,7 +28,11 @@ module EndGate.Tweening {
 
 //// [genericConstraintOnExtendedBuiltinTypes.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes2.js b/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes2.js
index 33394ee4fce..8ec4552b70d 100644
--- a/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes2.js
+++ b/tests/baselines/reference/genericConstraintOnExtendedBuiltinTypes2.js
@@ -27,7 +27,11 @@ module EndGate.Tweening {
 
 //// [genericConstraintOnExtendedBuiltinTypes2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericDerivedTypeWithSpecializedBase.js b/tests/baselines/reference/genericDerivedTypeWithSpecializedBase.js
index 413eed2a4c8..9da46a15ef7 100644
--- a/tests/baselines/reference/genericDerivedTypeWithSpecializedBase.js
+++ b/tests/baselines/reference/genericDerivedTypeWithSpecializedBase.js
@@ -14,7 +14,11 @@ x = y;  // error
 
 //// [genericDerivedTypeWithSpecializedBase.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.js b/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.js
index da81eaf5640..df9c113ceb5 100644
--- a/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.js
+++ b/tests/baselines/reference/genericDerivedTypeWithSpecializedBase2.js
@@ -14,7 +14,11 @@ x = y;  // error
 
 //// [genericDerivedTypeWithSpecializedBase2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericInheritedDefaultConstructors.js b/tests/baselines/reference/genericInheritedDefaultConstructors.js
index d7aaa6224ef..f287a5f934c 100644
--- a/tests/baselines/reference/genericInheritedDefaultConstructors.js
+++ b/tests/baselines/reference/genericInheritedDefaultConstructors.js
@@ -12,7 +12,11 @@ var c:Constructor<B<boolean>> = B; // shouldn't error here
 
 //// [genericInheritedDefaultConstructors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericPrototypeProperty2.js b/tests/baselines/reference/genericPrototypeProperty2.js
index 6ce627694ca..892e6cc0217 100644
--- a/tests/baselines/reference/genericPrototypeProperty2.js
+++ b/tests/baselines/reference/genericPrototypeProperty2.js
@@ -17,7 +17,11 @@ class MyEventWrapper extends BaseEventWrapper {
 
 //// [genericPrototypeProperty2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericPrototypeProperty3.js b/tests/baselines/reference/genericPrototypeProperty3.js
index a2817d82e9f..03755b28683 100644
--- a/tests/baselines/reference/genericPrototypeProperty3.js
+++ b/tests/baselines/reference/genericPrototypeProperty3.js
@@ -16,7 +16,11 @@ class MyEventWrapper extends BaseEventWrapper {
 
 //// [genericPrototypeProperty3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericRecursiveImplicitConstructorErrors2.js b/tests/baselines/reference/genericRecursiveImplicitConstructorErrors2.js
index 2fbb5f7ef50..f5c12bacce8 100644
--- a/tests/baselines/reference/genericRecursiveImplicitConstructorErrors2.js
+++ b/tests/baselines/reference/genericRecursiveImplicitConstructorErrors2.js
@@ -28,7 +28,11 @@ module TypeScript2 {
 
 //// [genericRecursiveImplicitConstructorErrors2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericRecursiveImplicitConstructorErrors3.js b/tests/baselines/reference/genericRecursiveImplicitConstructorErrors3.js
index c88dd78765a..3c680337351 100644
--- a/tests/baselines/reference/genericRecursiveImplicitConstructorErrors3.js
+++ b/tests/baselines/reference/genericRecursiveImplicitConstructorErrors3.js
@@ -32,7 +32,11 @@ module TypeScript {
 
 //// [genericRecursiveImplicitConstructorErrors3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericTypeAssertions2.js b/tests/baselines/reference/genericTypeAssertions2.js
index 25e4d3f3bae..d13e06a8ddd 100644
--- a/tests/baselines/reference/genericTypeAssertions2.js
+++ b/tests/baselines/reference/genericTypeAssertions2.js
@@ -15,7 +15,11 @@ var r5: A<number> = <A<number>>[]; // error
 
 //// [genericTypeAssertions2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericTypeAssertions4.js b/tests/baselines/reference/genericTypeAssertions4.js
index d54f37408a3..e1c4cab059c 100644
--- a/tests/baselines/reference/genericTypeAssertions4.js
+++ b/tests/baselines/reference/genericTypeAssertions4.js
@@ -27,7 +27,11 @@ function foo2<T extends A>(x: T) {
 
 //// [genericTypeAssertions4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericTypeAssertions6.js b/tests/baselines/reference/genericTypeAssertions6.js
index 6ace4b38a13..20a13d5718e 100644
--- a/tests/baselines/reference/genericTypeAssertions6.js
+++ b/tests/baselines/reference/genericTypeAssertions6.js
@@ -26,7 +26,11 @@ var c: A<Date, Date> = <A<Date, Date>>b;
 
 //// [genericTypeAssertions6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericTypeConstraints.js b/tests/baselines/reference/genericTypeConstraints.js
index 4aae830a0d1..b2332451507 100644
--- a/tests/baselines/reference/genericTypeConstraints.js
+++ b/tests/baselines/reference/genericTypeConstraints.js
@@ -15,7 +15,11 @@ class BarExtended extends Bar<FooExtended> {
 
 //// [genericTypeConstraints.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.js b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.js
index ec7029135a9..267666439b1 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.js
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.js
@@ -41,7 +41,11 @@ var k = <M.E>null;
 // it is an error to use a generic type without type arguments
 // all of these are errors 
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.js b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.js
index d3797663e0e..7fce4984d9c 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.js
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.js
@@ -41,7 +41,11 @@ var k = <M.E>null;
 // it is an error to use a generic type without type arguments
 // all of these are errors 
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/genericWithIndexerOfTypeParameterType2.js b/tests/baselines/reference/genericWithIndexerOfTypeParameterType2.js
index b5c3316ab12..444043fbeac 100644
--- a/tests/baselines/reference/genericWithIndexerOfTypeParameterType2.js
+++ b/tests/baselines/reference/genericWithIndexerOfTypeParameterType2.js
@@ -16,7 +16,11 @@ export class ListItem extends CollectionItem {
 
 //// [genericWithIndexerOfTypeParameterType2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/heterogeneousArrayLiterals.js b/tests/baselines/reference/heterogeneousArrayLiterals.js
index 43ec9a09587..6a9f8ae1453 100644
--- a/tests/baselines/reference/heterogeneousArrayLiterals.js
+++ b/tests/baselines/reference/heterogeneousArrayLiterals.js
@@ -134,7 +134,11 @@ function foo4<T extends Base, U extends Base>(t: T, u: U) {
 //// [heterogeneousArrayLiterals.js]
 // type of an array is the best common type of its elements (plus its contextual type if it exists)
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/ifDoWhileStatements.js b/tests/baselines/reference/ifDoWhileStatements.js
index 8d1ad1a834f..fea4eee36fa 100644
--- a/tests/baselines/reference/ifDoWhileStatements.js
+++ b/tests/baselines/reference/ifDoWhileStatements.js
@@ -165,7 +165,11 @@ do { }while(fn)
 
 //// [ifDoWhileStatements.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/illegalSuperCallsInConstructor.js b/tests/baselines/reference/illegalSuperCallsInConstructor.js
index 5299bac5eb3..3de32da45c0 100644
--- a/tests/baselines/reference/illegalSuperCallsInConstructor.js
+++ b/tests/baselines/reference/illegalSuperCallsInConstructor.js
@@ -22,7 +22,11 @@ class Derived extends Base {
 
 //// [illegalSuperCallsInConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/implementClausePrecedingExtends.js b/tests/baselines/reference/implementClausePrecedingExtends.js
index 669a6794618..5d717358863 100644
--- a/tests/baselines/reference/implementClausePrecedingExtends.js
+++ b/tests/baselines/reference/implementClausePrecedingExtends.js
@@ -4,7 +4,11 @@ class D implements C extends C { }
 
 //// [implementClausePrecedingExtends.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/implementingAnInterfaceExtendingClassWithPrivates2.js b/tests/baselines/reference/implementingAnInterfaceExtendingClassWithPrivates2.js
index 5d93d2b04a4..87b22c74f6b 100644
--- a/tests/baselines/reference/implementingAnInterfaceExtendingClassWithPrivates2.js
+++ b/tests/baselines/reference/implementingAnInterfaceExtendingClassWithPrivates2.js
@@ -87,7 +87,11 @@ module M2 {
 
 //// [implementingAnInterfaceExtendingClassWithPrivates2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/implementingAnInterfaceExtendingClassWithProtecteds.js b/tests/baselines/reference/implementingAnInterfaceExtendingClassWithProtecteds.js
index 082b9d801dc..68ecf9ede2b 100644
--- a/tests/baselines/reference/implementingAnInterfaceExtendingClassWithProtecteds.js
+++ b/tests/baselines/reference/implementingAnInterfaceExtendingClassWithProtecteds.js
@@ -43,7 +43,11 @@ class Bar8 extends Foo implements I {
 
 //// [implementingAnInterfaceExtendingClassWithProtecteds.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/importAsBaseClass.js b/tests/baselines/reference/importAsBaseClass.js
index f61703de5f0..ea7c757e035 100644
--- a/tests/baselines/reference/importAsBaseClass.js
+++ b/tests/baselines/reference/importAsBaseClass.js
@@ -22,7 +22,11 @@ exports.Greeter = Greeter;
 //// [importAsBaseClass_1.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/importHelpers.js b/tests/baselines/reference/importHelpers.js
index ec294a342de..0a9dcd4a780 100644
--- a/tests/baselines/reference/importHelpers.js
+++ b/tests/baselines/reference/importHelpers.js
@@ -69,7 +69,11 @@ C = tslib_1.__decorate([
 ], C);
 //// [script.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/importHelpersNoHelpers.js b/tests/baselines/reference/importHelpersNoHelpers.js
index 3a2e4823337..c7c575f5402 100644
--- a/tests/baselines/reference/importHelpersNoHelpers.js
+++ b/tests/baselines/reference/importHelpersNoHelpers.js
@@ -71,7 +71,11 @@ var y = tslib_1.__assign({}, o);
 var x = tslib_1.__rest(y, []);
 //// [script.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/importHelpersNoModule.js b/tests/baselines/reference/importHelpersNoModule.js
index 991733f4b37..212bc7a54f7 100644
--- a/tests/baselines/reference/importHelpersNoModule.js
+++ b/tests/baselines/reference/importHelpersNoModule.js
@@ -61,7 +61,11 @@ C = tslib_1.__decorate([
 ], C);
 //// [script.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/importShadowsGlobalName.js b/tests/baselines/reference/importShadowsGlobalName.js
index abdf7e28cbb..8431a87ce03 100644
--- a/tests/baselines/reference/importShadowsGlobalName.js
+++ b/tests/baselines/reference/importShadowsGlobalName.js
@@ -22,7 +22,11 @@ define(["require", "exports"], function (require, exports) {
 });
 //// [Bar.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/importUsedInExtendsList1.js b/tests/baselines/reference/importUsedInExtendsList1.js
index 941436e7e75..f44a0fcfce4 100644
--- a/tests/baselines/reference/importUsedInExtendsList1.js
+++ b/tests/baselines/reference/importUsedInExtendsList1.js
@@ -22,7 +22,11 @@ exports.Super = Super;
 //// [importUsedInExtendsList1_1.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/indexerConstraints2.js b/tests/baselines/reference/indexerConstraints2.js
index 81bb114e394..45980beb09c 100644
--- a/tests/baselines/reference/indexerConstraints2.js
+++ b/tests/baselines/reference/indexerConstraints2.js
@@ -30,7 +30,11 @@ class K extends J {
 
 //// [indexerConstraints2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/indirectSelfReference.js b/tests/baselines/reference/indirectSelfReference.js
index a61a14a2d6b..931525d4b6b 100644
--- a/tests/baselines/reference/indirectSelfReference.js
+++ b/tests/baselines/reference/indirectSelfReference.js
@@ -4,7 +4,11 @@ class b extends a{ }
 
 //// [indirectSelfReference.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/indirectSelfReferenceGeneric.js b/tests/baselines/reference/indirectSelfReferenceGeneric.js
index 989a02b1943..e7d2bdf2a2b 100644
--- a/tests/baselines/reference/indirectSelfReferenceGeneric.js
+++ b/tests/baselines/reference/indirectSelfReferenceGeneric.js
@@ -4,7 +4,11 @@ class b<T> extends a<T> { }
 
 //// [indirectSelfReferenceGeneric.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/infinitelyExpandingTypesNonGenericBase.js b/tests/baselines/reference/infinitelyExpandingTypesNonGenericBase.js
index 7336e2c0f69..96a8e84ff60 100644
--- a/tests/baselines/reference/infinitelyExpandingTypesNonGenericBase.js
+++ b/tests/baselines/reference/infinitelyExpandingTypesNonGenericBase.js
@@ -26,7 +26,11 @@ o(A);
 
 //// [infinitelyExpandingTypesNonGenericBase.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritFromGenericTypeParameter.js b/tests/baselines/reference/inheritFromGenericTypeParameter.js
index 57ad5b71bd8..d95150bbccc 100644
--- a/tests/baselines/reference/inheritFromGenericTypeParameter.js
+++ b/tests/baselines/reference/inheritFromGenericTypeParameter.js
@@ -4,7 +4,11 @@ interface I<T> extends T { }
 
 //// [inheritFromGenericTypeParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritSameNamePrivatePropertiesFromSameOrigin.js b/tests/baselines/reference/inheritSameNamePrivatePropertiesFromSameOrigin.js
index 679e91dc38a..b1224117ede 100644
--- a/tests/baselines/reference/inheritSameNamePrivatePropertiesFromSameOrigin.js
+++ b/tests/baselines/reference/inheritSameNamePrivatePropertiesFromSameOrigin.js
@@ -12,7 +12,11 @@ interface A extends C, C2 { // ok
 
 //// [inheritSameNamePrivatePropertiesFromSameOrigin.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritance.js b/tests/baselines/reference/inheritance.js
index 01fdd0a3d67..b9a7c5a336f 100644
--- a/tests/baselines/reference/inheritance.js
+++ b/tests/baselines/reference/inheritance.js
@@ -36,7 +36,11 @@ class Baad extends Good {
 
 //// [inheritance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritance1.js b/tests/baselines/reference/inheritance1.js
index c33c73a6e60..0e5bff48a3b 100644
--- a/tests/baselines/reference/inheritance1.js
+++ b/tests/baselines/reference/inheritance1.js
@@ -63,7 +63,11 @@ l1 = c;
 
 //// [inheritance1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollision.js b/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollision.js
index 180f48f613c..bd4b70f7938 100644
--- a/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollision.js
+++ b/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollision.js
@@ -12,7 +12,11 @@ class C extends B {
 
 //// [inheritanceGrandParentPrivateMemberCollision.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollisionWithPublicMember.js b/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollisionWithPublicMember.js
index 73121951e7c..d72f85cf599 100644
--- a/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollisionWithPublicMember.js
+++ b/tests/baselines/reference/inheritanceGrandParentPrivateMemberCollisionWithPublicMember.js
@@ -12,7 +12,11 @@ class C extends B {
 
 //// [inheritanceGrandParentPrivateMemberCollisionWithPublicMember.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceGrandParentPublicMemberCollisionWithPrivateMember.js b/tests/baselines/reference/inheritanceGrandParentPublicMemberCollisionWithPrivateMember.js
index 60183c5749e..c6b32f6bc5d 100644
--- a/tests/baselines/reference/inheritanceGrandParentPublicMemberCollisionWithPrivateMember.js
+++ b/tests/baselines/reference/inheritanceGrandParentPublicMemberCollisionWithPrivateMember.js
@@ -12,7 +12,11 @@ class C extends B {
 
 //// [inheritanceGrandParentPublicMemberCollisionWithPrivateMember.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberAccessorOverridingAccessor.js b/tests/baselines/reference/inheritanceMemberAccessorOverridingAccessor.js
index fc1ff97e8cf..fdc53cc7e9c 100644
--- a/tests/baselines/reference/inheritanceMemberAccessorOverridingAccessor.js
+++ b/tests/baselines/reference/inheritanceMemberAccessorOverridingAccessor.js
@@ -19,7 +19,11 @@ class b extends a {
 
 //// [inheritanceMemberAccessorOverridingAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberAccessorOverridingMethod.js b/tests/baselines/reference/inheritanceMemberAccessorOverridingMethod.js
index 0ba2a70f257..13e624a9d57 100644
--- a/tests/baselines/reference/inheritanceMemberAccessorOverridingMethod.js
+++ b/tests/baselines/reference/inheritanceMemberAccessorOverridingMethod.js
@@ -16,7 +16,11 @@ class b extends a {
 
 //// [inheritanceMemberAccessorOverridingMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberAccessorOverridingProperty.js b/tests/baselines/reference/inheritanceMemberAccessorOverridingProperty.js
index 26c911694a2..243992d5bd3 100644
--- a/tests/baselines/reference/inheritanceMemberAccessorOverridingProperty.js
+++ b/tests/baselines/reference/inheritanceMemberAccessorOverridingProperty.js
@@ -14,7 +14,11 @@ class b extends a {
 
 //// [inheritanceMemberAccessorOverridingProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberFuncOverridingAccessor.js b/tests/baselines/reference/inheritanceMemberFuncOverridingAccessor.js
index d0dfcc5923a..001f7b888e3 100644
--- a/tests/baselines/reference/inheritanceMemberFuncOverridingAccessor.js
+++ b/tests/baselines/reference/inheritanceMemberFuncOverridingAccessor.js
@@ -16,7 +16,11 @@ class b extends a {
 
 //// [inheritanceMemberFuncOverridingAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberFuncOverridingMethod.js b/tests/baselines/reference/inheritanceMemberFuncOverridingMethod.js
index 64e5e923178..33a35428b8e 100644
--- a/tests/baselines/reference/inheritanceMemberFuncOverridingMethod.js
+++ b/tests/baselines/reference/inheritanceMemberFuncOverridingMethod.js
@@ -13,7 +13,11 @@ class b extends a {
 
 //// [inheritanceMemberFuncOverridingMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberFuncOverridingProperty.js b/tests/baselines/reference/inheritanceMemberFuncOverridingProperty.js
index f3835a78f14..0675aead222 100644
--- a/tests/baselines/reference/inheritanceMemberFuncOverridingProperty.js
+++ b/tests/baselines/reference/inheritanceMemberFuncOverridingProperty.js
@@ -11,7 +11,11 @@ class b extends a {
 
 //// [inheritanceMemberFuncOverridingProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberPropertyOverridingAccessor.js b/tests/baselines/reference/inheritanceMemberPropertyOverridingAccessor.js
index 82fc4906ca6..ec3e8519e62 100644
--- a/tests/baselines/reference/inheritanceMemberPropertyOverridingAccessor.js
+++ b/tests/baselines/reference/inheritanceMemberPropertyOverridingAccessor.js
@@ -15,7 +15,11 @@ class b extends a {
 
 //// [inheritanceMemberPropertyOverridingAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberPropertyOverridingMethod.js b/tests/baselines/reference/inheritanceMemberPropertyOverridingMethod.js
index e13a111fef9..e2e1d734001 100644
--- a/tests/baselines/reference/inheritanceMemberPropertyOverridingMethod.js
+++ b/tests/baselines/reference/inheritanceMemberPropertyOverridingMethod.js
@@ -11,7 +11,11 @@ class b extends a {
 
 //// [inheritanceMemberPropertyOverridingMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceMemberPropertyOverridingProperty.js b/tests/baselines/reference/inheritanceMemberPropertyOverridingProperty.js
index b6496085a61..50d6b108588 100644
--- a/tests/baselines/reference/inheritanceMemberPropertyOverridingProperty.js
+++ b/tests/baselines/reference/inheritanceMemberPropertyOverridingProperty.js
@@ -9,7 +9,11 @@ class b extends a {
 
 //// [inheritanceMemberPropertyOverridingProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceOfGenericConstructorMethod1.js b/tests/baselines/reference/inheritanceOfGenericConstructorMethod1.js
index ac99c90e829..871acd1d624 100644
--- a/tests/baselines/reference/inheritanceOfGenericConstructorMethod1.js
+++ b/tests/baselines/reference/inheritanceOfGenericConstructorMethod1.js
@@ -9,7 +9,11 @@ var b3 = new B<Date>(); // error, could not select overload for 'new' expression
 
 //// [inheritanceOfGenericConstructorMethod1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceOfGenericConstructorMethod2.js b/tests/baselines/reference/inheritanceOfGenericConstructorMethod2.js
index 406675d88d9..72f12c8f81f 100644
--- a/tests/baselines/reference/inheritanceOfGenericConstructorMethod2.js
+++ b/tests/baselines/reference/inheritanceOfGenericConstructorMethod2.js
@@ -16,7 +16,11 @@ var n3 = new N.D2(); // no error, D2<any>
 
 //// [inheritanceOfGenericConstructorMethod2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticAccessorOverridingAccessor.js b/tests/baselines/reference/inheritanceStaticAccessorOverridingAccessor.js
index 3faa8f8388d..c58a0643a06 100644
--- a/tests/baselines/reference/inheritanceStaticAccessorOverridingAccessor.js
+++ b/tests/baselines/reference/inheritanceStaticAccessorOverridingAccessor.js
@@ -19,7 +19,11 @@ class b extends a {
 
 //// [inheritanceStaticAccessorOverridingAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticAccessorOverridingMethod.js b/tests/baselines/reference/inheritanceStaticAccessorOverridingMethod.js
index 543651ea6f0..beba3dbdf5e 100644
--- a/tests/baselines/reference/inheritanceStaticAccessorOverridingMethod.js
+++ b/tests/baselines/reference/inheritanceStaticAccessorOverridingMethod.js
@@ -16,7 +16,11 @@ class b extends a {
 
 //// [inheritanceStaticAccessorOverridingMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticAccessorOverridingProperty.js b/tests/baselines/reference/inheritanceStaticAccessorOverridingProperty.js
index 5053cd3946a..d3f4b177e95 100644
--- a/tests/baselines/reference/inheritanceStaticAccessorOverridingProperty.js
+++ b/tests/baselines/reference/inheritanceStaticAccessorOverridingProperty.js
@@ -14,7 +14,11 @@ class b extends a {
 
 //// [inheritanceStaticAccessorOverridingProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticFuncOverridingAccessor.js b/tests/baselines/reference/inheritanceStaticFuncOverridingAccessor.js
index 6090bd4f74f..d86d08e7add 100644
--- a/tests/baselines/reference/inheritanceStaticFuncOverridingAccessor.js
+++ b/tests/baselines/reference/inheritanceStaticFuncOverridingAccessor.js
@@ -16,7 +16,11 @@ class b extends a {
 
 //// [inheritanceStaticFuncOverridingAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticFuncOverridingAccessorOfFuncType.js b/tests/baselines/reference/inheritanceStaticFuncOverridingAccessorOfFuncType.js
index 5213eae20dd..1decf45e015 100644
--- a/tests/baselines/reference/inheritanceStaticFuncOverridingAccessorOfFuncType.js
+++ b/tests/baselines/reference/inheritanceStaticFuncOverridingAccessorOfFuncType.js
@@ -13,7 +13,11 @@ class b extends a {
 
 //// [inheritanceStaticFuncOverridingAccessorOfFuncType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticFuncOverridingMethod.js b/tests/baselines/reference/inheritanceStaticFuncOverridingMethod.js
index 4d85f383ef6..e9ea5d2f6a1 100644
--- a/tests/baselines/reference/inheritanceStaticFuncOverridingMethod.js
+++ b/tests/baselines/reference/inheritanceStaticFuncOverridingMethod.js
@@ -13,7 +13,11 @@ class b extends a {
 
 //// [inheritanceStaticFuncOverridingMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticFuncOverridingProperty.js b/tests/baselines/reference/inheritanceStaticFuncOverridingProperty.js
index a548d70861b..dd2260ecf31 100644
--- a/tests/baselines/reference/inheritanceStaticFuncOverridingProperty.js
+++ b/tests/baselines/reference/inheritanceStaticFuncOverridingProperty.js
@@ -11,7 +11,11 @@ class b extends a {
 
 //// [inheritanceStaticFuncOverridingProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticFuncOverridingPropertyOfFuncType.js b/tests/baselines/reference/inheritanceStaticFuncOverridingPropertyOfFuncType.js
index 9f2a7acfd14..9a555ce218f 100644
--- a/tests/baselines/reference/inheritanceStaticFuncOverridingPropertyOfFuncType.js
+++ b/tests/baselines/reference/inheritanceStaticFuncOverridingPropertyOfFuncType.js
@@ -11,7 +11,11 @@ class b extends a {
 
 //// [inheritanceStaticFuncOverridingPropertyOfFuncType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticFunctionOverridingInstanceProperty.js b/tests/baselines/reference/inheritanceStaticFunctionOverridingInstanceProperty.js
index c489493375e..e357eb6e01f 100644
--- a/tests/baselines/reference/inheritanceStaticFunctionOverridingInstanceProperty.js
+++ b/tests/baselines/reference/inheritanceStaticFunctionOverridingInstanceProperty.js
@@ -11,7 +11,11 @@ class b extends a {
 
 //// [inheritanceStaticFunctionOverridingInstanceProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticMembersCompatible.js b/tests/baselines/reference/inheritanceStaticMembersCompatible.js
index b57ada54212..044db517290 100644
--- a/tests/baselines/reference/inheritanceStaticMembersCompatible.js
+++ b/tests/baselines/reference/inheritanceStaticMembersCompatible.js
@@ -9,7 +9,11 @@ class b extends a {
 
 //// [inheritanceStaticMembersCompatible.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticMembersIncompatible.js b/tests/baselines/reference/inheritanceStaticMembersIncompatible.js
index 11e8e0117db..0c21f4a1af5 100644
--- a/tests/baselines/reference/inheritanceStaticMembersIncompatible.js
+++ b/tests/baselines/reference/inheritanceStaticMembersIncompatible.js
@@ -9,7 +9,11 @@ class b extends a {
 
 //// [inheritanceStaticMembersIncompatible.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticPropertyOverridingAccessor.js b/tests/baselines/reference/inheritanceStaticPropertyOverridingAccessor.js
index 7283ee4dbb0..de05071c116 100644
--- a/tests/baselines/reference/inheritanceStaticPropertyOverridingAccessor.js
+++ b/tests/baselines/reference/inheritanceStaticPropertyOverridingAccessor.js
@@ -14,7 +14,11 @@ class b extends a {
 
 //// [inheritanceStaticPropertyOverridingAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticPropertyOverridingMethod.js b/tests/baselines/reference/inheritanceStaticPropertyOverridingMethod.js
index e9308f977db..4c1ca7e00cb 100644
--- a/tests/baselines/reference/inheritanceStaticPropertyOverridingMethod.js
+++ b/tests/baselines/reference/inheritanceStaticPropertyOverridingMethod.js
@@ -11,7 +11,11 @@ class b extends a {
 
 //// [inheritanceStaticPropertyOverridingMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritanceStaticPropertyOverridingProperty.js b/tests/baselines/reference/inheritanceStaticPropertyOverridingProperty.js
index 4feb0e06b8c..a351a84d98b 100644
--- a/tests/baselines/reference/inheritanceStaticPropertyOverridingProperty.js
+++ b/tests/baselines/reference/inheritanceStaticPropertyOverridingProperty.js
@@ -9,7 +9,11 @@ class b extends a {
 
 //// [inheritanceStaticPropertyOverridingProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritedConstructorWithRestParams.js b/tests/baselines/reference/inheritedConstructorWithRestParams.js
index 4d3b055dcdb..e9f362ead42 100644
--- a/tests/baselines/reference/inheritedConstructorWithRestParams.js
+++ b/tests/baselines/reference/inheritedConstructorWithRestParams.js
@@ -16,7 +16,11 @@ new Derived(3);
 
 //// [inheritedConstructorWithRestParams.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritedConstructorWithRestParams2.js b/tests/baselines/reference/inheritedConstructorWithRestParams2.js
index 146677ff09c..3d89d237ad5 100644
--- a/tests/baselines/reference/inheritedConstructorWithRestParams2.js
+++ b/tests/baselines/reference/inheritedConstructorWithRestParams2.js
@@ -36,7 +36,11 @@ new Derived("", 3, "", "");
 
 //// [inheritedConstructorWithRestParams2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/inheritedModuleMembersForClodule.js b/tests/baselines/reference/inheritedModuleMembersForClodule.js
index 666f4d703be..512d8bbca57 100644
--- a/tests/baselines/reference/inheritedModuleMembersForClodule.js
+++ b/tests/baselines/reference/inheritedModuleMembersForClodule.js
@@ -23,7 +23,11 @@ class E extends D {
 
 //// [inheritedModuleMembersForClodule.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/instanceOfAssignability.js b/tests/baselines/reference/instanceOfAssignability.js
index 1492a9f919b..4f7b0bead56 100644
--- a/tests/baselines/reference/instanceOfAssignability.js
+++ b/tests/baselines/reference/instanceOfAssignability.js
@@ -91,7 +91,11 @@ function fn8(x: Alpha|Beta|Gamma) {
 
 //// [instanceOfAssignability.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/instancePropertiesInheritedIntoClassType.js b/tests/baselines/reference/instancePropertiesInheritedIntoClassType.js
index a421814ea2d..57c7e5161b2 100644
--- a/tests/baselines/reference/instancePropertiesInheritedIntoClassType.js
+++ b/tests/baselines/reference/instancePropertiesInheritedIntoClassType.js
@@ -44,7 +44,11 @@ module Generic {
 
 //// [instancePropertiesInheritedIntoClassType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/instanceSubtypeCheck2.js b/tests/baselines/reference/instanceSubtypeCheck2.js
index c6c657aa82e..7f4b0803382 100644
--- a/tests/baselines/reference/instanceSubtypeCheck2.js
+++ b/tests/baselines/reference/instanceSubtypeCheck2.js
@@ -9,7 +9,11 @@ class C2<T> extends C1<T> {
 
 //// [instanceSubtypeCheck2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/instanceofWithStructurallyIdenticalTypes.js b/tests/baselines/reference/instanceofWithStructurallyIdenticalTypes.js
index 46c842c86a7..59ea1270155 100644
--- a/tests/baselines/reference/instanceofWithStructurallyIdenticalTypes.js
+++ b/tests/baselines/reference/instanceofWithStructurallyIdenticalTypes.js
@@ -73,7 +73,11 @@ function goo(x: A) {
 //// [instanceofWithStructurallyIdenticalTypes.js]
 // Repro from #7271
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/instantiatedReturnTypeContravariance.js b/tests/baselines/reference/instantiatedReturnTypeContravariance.js
index ac3470cb288..338a60610a0 100644
--- a/tests/baselines/reference/instantiatedReturnTypeContravariance.js
+++ b/tests/baselines/reference/instantiatedReturnTypeContravariance.js
@@ -32,7 +32,11 @@ return null;
 
 //// [instantiatedReturnTypeContravariance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/interfaceClassMerging.js b/tests/baselines/reference/interfaceClassMerging.js
index 931d94f6eda..36e4719549a 100644
--- a/tests/baselines/reference/interfaceClassMerging.js
+++ b/tests/baselines/reference/interfaceClassMerging.js
@@ -42,7 +42,11 @@ obj = bar;
 
 //// [interfaceClassMerging.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/interfaceClassMerging2.js b/tests/baselines/reference/interfaceClassMerging2.js
index c0c9b17b3e8..f230544e492 100644
--- a/tests/baselines/reference/interfaceClassMerging2.js
+++ b/tests/baselines/reference/interfaceClassMerging2.js
@@ -38,7 +38,11 @@ foo = bar;
 
 //// [interfaceClassMerging2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/interfaceExtendsClass1.js b/tests/baselines/reference/interfaceExtendsClass1.js
index 85b4a42302d..0afae83d4b9 100644
--- a/tests/baselines/reference/interfaceExtendsClass1.js
+++ b/tests/baselines/reference/interfaceExtendsClass1.js
@@ -20,7 +20,11 @@ class Location {
 
 //// [interfaceExtendsClass1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/interfaceExtendsClassWithPrivate1.js b/tests/baselines/reference/interfaceExtendsClassWithPrivate1.js
index 05ae7d83678..0b493aded80 100644
--- a/tests/baselines/reference/interfaceExtendsClassWithPrivate1.js
+++ b/tests/baselines/reference/interfaceExtendsClassWithPrivate1.js
@@ -29,7 +29,11 @@ d = c; // error
 
 //// [interfaceExtendsClassWithPrivate1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/interfaceExtendsClassWithPrivate2.js b/tests/baselines/reference/interfaceExtendsClassWithPrivate2.js
index a1ff0fff763..699b924a854 100644
--- a/tests/baselines/reference/interfaceExtendsClassWithPrivate2.js
+++ b/tests/baselines/reference/interfaceExtendsClassWithPrivate2.js
@@ -25,7 +25,11 @@ class D2 extends C implements I { // error
 
 //// [interfaceExtendsClassWithPrivate2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/interfaceImplementation8.js b/tests/baselines/reference/interfaceImplementation8.js
index 2193189eaf1..04f341d1f06 100644
--- a/tests/baselines/reference/interfaceImplementation8.js
+++ b/tests/baselines/reference/interfaceImplementation8.js
@@ -42,7 +42,11 @@ class C8 extends C7 implements i2{
 
 //// [interfaceImplementation8.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/invalidModuleWithStatementsOfEveryKind.js b/tests/baselines/reference/invalidModuleWithStatementsOfEveryKind.js
index dc4284495b1..8fa200638e4 100644
--- a/tests/baselines/reference/invalidModuleWithStatementsOfEveryKind.js
+++ b/tests/baselines/reference/invalidModuleWithStatementsOfEveryKind.js
@@ -81,7 +81,11 @@ module YYY4 {
 //// [invalidModuleWithStatementsOfEveryKind.js]
 // All of these should be an error
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/invalidMultipleVariableDeclarations.js b/tests/baselines/reference/invalidMultipleVariableDeclarations.js
index 2117e176f08..3380d5847a9 100644
--- a/tests/baselines/reference/invalidMultipleVariableDeclarations.js
+++ b/tests/baselines/reference/invalidMultipleVariableDeclarations.js
@@ -55,7 +55,11 @@ var m = M.A;
 
 //// [invalidMultipleVariableDeclarations.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/invalidReturnStatements.js b/tests/baselines/reference/invalidReturnStatements.js
index 8f1adc05fa6..01982b322bb 100644
--- a/tests/baselines/reference/invalidReturnStatements.js
+++ b/tests/baselines/reference/invalidReturnStatements.js
@@ -22,7 +22,11 @@ function fn11(): D { return new C(); }
 
 //// [invalidReturnStatements.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/isolatedModulesImportExportElision.js b/tests/baselines/reference/isolatedModulesImportExportElision.js
index e98932901e3..747e69d7c59 100644
--- a/tests/baselines/reference/isolatedModulesImportExportElision.js
+++ b/tests/baselines/reference/isolatedModulesImportExportElision.js
@@ -16,7 +16,11 @@ export var z = x;
 //// [file1.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/jsxViaImport.js b/tests/baselines/reference/jsxViaImport.js
index 99b9229f2a5..61e196daaa4 100644
--- a/tests/baselines/reference/jsxViaImport.js
+++ b/tests/baselines/reference/jsxViaImport.js
@@ -26,7 +26,11 @@ class TestComponent extends React.Component<any, {}> {
 //// [consumer.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/keyofAndIndexedAccess.js b/tests/baselines/reference/keyofAndIndexedAccess.js
index 50bb51dbae7..319875eef2c 100644
--- a/tests/baselines/reference/keyofAndIndexedAccess.js
+++ b/tests/baselines/reference/keyofAndIndexedAccess.js
@@ -295,7 +295,11 @@ var hashOfEmpty2 = on({ test: (x: boolean) => {} });  // { test: boolean }
 
 //// [keyofAndIndexedAccess.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/lambdaArgCrash.js b/tests/baselines/reference/lambdaArgCrash.js
index 911232722bd..c4343a67452 100644
--- a/tests/baselines/reference/lambdaArgCrash.js
+++ b/tests/baselines/reference/lambdaArgCrash.js
@@ -36,7 +36,11 @@ class ItemSetEvent extends Event {
 
 //// [lambdaArgCrash.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/lift.js b/tests/baselines/reference/lift.js
index cd6f4fffd00..44932a3ad14 100644
--- a/tests/baselines/reference/lift.js
+++ b/tests/baselines/reference/lift.js
@@ -19,7 +19,11 @@ class C extends B {
 
 //// [lift.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/localTypes1.js b/tests/baselines/reference/localTypes1.js
index a887a3e07b0..2a3510860ef 100644
--- a/tests/baselines/reference/localTypes1.js
+++ b/tests/baselines/reference/localTypes1.js
@@ -143,7 +143,11 @@ function f6() {
 
 //// [localTypes1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/m7Bugs.js b/tests/baselines/reference/m7Bugs.js
index 078c77c5e3c..0ae1f77a62a 100644
--- a/tests/baselines/reference/m7Bugs.js
+++ b/tests/baselines/reference/m7Bugs.js
@@ -28,7 +28,11 @@ var y3: C1 = <C1> {};
 
 //// [m7Bugs.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/mergedDeclarations5.js b/tests/baselines/reference/mergedDeclarations5.js
index f731d4de428..d8426a5ce28 100644
--- a/tests/baselines/reference/mergedDeclarations5.js
+++ b/tests/baselines/reference/mergedDeclarations5.js
@@ -20,7 +20,11 @@ var A = (function () {
 }());
 //// [b.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/mergedDeclarations6.js b/tests/baselines/reference/mergedDeclarations6.js
index 42ef5702061..c573190dc8b 100644
--- a/tests/baselines/reference/mergedDeclarations6.js
+++ b/tests/baselines/reference/mergedDeclarations6.js
@@ -38,7 +38,11 @@ define(["require", "exports"], function (require, exports) {
 });
 //// [b.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/mergedInheritedClassInterface.js b/tests/baselines/reference/mergedInheritedClassInterface.js
index 38d4f94adde..ec1b72bf5d7 100644
--- a/tests/baselines/reference/mergedInheritedClassInterface.js
+++ b/tests/baselines/reference/mergedInheritedClassInterface.js
@@ -48,7 +48,11 @@ grandchild.method2();
 
 //// [mergedInheritedClassInterface.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/mergedInterfacesWithInheritedPrivates2.js b/tests/baselines/reference/mergedInterfacesWithInheritedPrivates2.js
index fd3d2da41e3..ac82060f270 100644
--- a/tests/baselines/reference/mergedInterfacesWithInheritedPrivates2.js
+++ b/tests/baselines/reference/mergedInterfacesWithInheritedPrivates2.js
@@ -33,7 +33,11 @@ var r2 = a.w; // error
 
 //// [mergedInterfacesWithInheritedPrivates2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/mergedInterfacesWithInheritedPrivates3.js b/tests/baselines/reference/mergedInterfacesWithInheritedPrivates3.js
index 1c8ba88d786..31c3deff6d1 100644
--- a/tests/baselines/reference/mergedInterfacesWithInheritedPrivates3.js
+++ b/tests/baselines/reference/mergedInterfacesWithInheritedPrivates3.js
@@ -40,7 +40,11 @@ module M {
 
 //// [mergedInterfacesWithInheritedPrivates3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/missingPropertiesOfClassExpression.js b/tests/baselines/reference/missingPropertiesOfClassExpression.js
index 8df4153b72d..aa832f39416 100644
--- a/tests/baselines/reference/missingPropertiesOfClassExpression.js
+++ b/tests/baselines/reference/missingPropertiesOfClassExpression.js
@@ -8,7 +8,11 @@ class George extends class { reset() { return this.y; } } {
 
 //// [missingPropertiesOfClassExpression.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/moduleAsBaseType.js b/tests/baselines/reference/moduleAsBaseType.js
index a4caea585ac..00a4f417804 100644
--- a/tests/baselines/reference/moduleAsBaseType.js
+++ b/tests/baselines/reference/moduleAsBaseType.js
@@ -6,7 +6,11 @@ class C2 implements M { }
 
 //// [moduleAsBaseType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/moduleImportedForTypeArgumentPosition.js b/tests/baselines/reference/moduleImportedForTypeArgumentPosition.js
index bf074378d4b..a12c2af9439 100644
--- a/tests/baselines/reference/moduleImportedForTypeArgumentPosition.js
+++ b/tests/baselines/reference/moduleImportedForTypeArgumentPosition.js
@@ -17,7 +17,11 @@ define(["require", "exports"], function (require, exports) {
 });
 //// [moduleImportedForTypeArgumentPosition_1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/moduleWithStatementsOfEveryKind.js b/tests/baselines/reference/moduleWithStatementsOfEveryKind.js
index 6efcddf7201..7a36ad10376 100644
--- a/tests/baselines/reference/moduleWithStatementsOfEveryKind.js
+++ b/tests/baselines/reference/moduleWithStatementsOfEveryKind.js
@@ -60,7 +60,11 @@ module Y {
 
 //// [moduleWithStatementsOfEveryKind.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/multipleInheritance.js b/tests/baselines/reference/multipleInheritance.js
index d05f10568ad..4122bcb40ee 100644
--- a/tests/baselines/reference/multipleInheritance.js
+++ b/tests/baselines/reference/multipleInheritance.js
@@ -40,7 +40,11 @@ class Baad extends Good {
 
 //// [multipleInheritance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/mutuallyRecursiveGenericBaseTypes2.js b/tests/baselines/reference/mutuallyRecursiveGenericBaseTypes2.js
index 570a93e8534..1ac0e7db55d 100644
--- a/tests/baselines/reference/mutuallyRecursiveGenericBaseTypes2.js
+++ b/tests/baselines/reference/mutuallyRecursiveGenericBaseTypes2.js
@@ -12,7 +12,11 @@ var test = new foo<string>();
 
 //// [mutuallyRecursiveGenericBaseTypes2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/noImplicitAnyMissingGetAccessor.js b/tests/baselines/reference/noImplicitAnyMissingGetAccessor.js
index 78ea4e74a97..e08985796c3 100644
--- a/tests/baselines/reference/noImplicitAnyMissingGetAccessor.js
+++ b/tests/baselines/reference/noImplicitAnyMissingGetAccessor.js
@@ -14,7 +14,11 @@ class Child extends Parent {
 
 //// [noImplicitAnyMissingGetAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/noImplicitAnyMissingSetAccessor.js b/tests/baselines/reference/noImplicitAnyMissingSetAccessor.js
index 64c480cc8e1..45cf29fd567 100644
--- a/tests/baselines/reference/noImplicitAnyMissingSetAccessor.js
+++ b/tests/baselines/reference/noImplicitAnyMissingSetAccessor.js
@@ -13,7 +13,11 @@ class Child extends Parent {
 
 //// [noImplicitAnyMissingSetAccessor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/nonGenericClassExtendingGenericClassWithAny.js b/tests/baselines/reference/nonGenericClassExtendingGenericClassWithAny.js
index 33f7e696126..270ea7f3bfc 100644
--- a/tests/baselines/reference/nonGenericClassExtendingGenericClassWithAny.js
+++ b/tests/baselines/reference/nonGenericClassExtendingGenericClassWithAny.js
@@ -7,7 +7,11 @@ class Bar extends Foo<any> { } // Valid
 
 //// [nonGenericClassExtendingGenericClassWithAny.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/numericIndexerConstrainsPropertyDeclarations2.js b/tests/baselines/reference/numericIndexerConstrainsPropertyDeclarations2.js
index c8ec0d9da78..2f2be923f17 100644
--- a/tests/baselines/reference/numericIndexerConstrainsPropertyDeclarations2.js
+++ b/tests/baselines/reference/numericIndexerConstrainsPropertyDeclarations2.js
@@ -48,7 +48,11 @@ var b: { [x: number]: A } = {
 //// [numericIndexerConstrainsPropertyDeclarations2.js]
 // String indexer providing a constraint of a user defined type
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/numericIndexerConstraint3.js b/tests/baselines/reference/numericIndexerConstraint3.js
index 02b54a2bbad..85556b4c83d 100644
--- a/tests/baselines/reference/numericIndexerConstraint3.js
+++ b/tests/baselines/reference/numericIndexerConstraint3.js
@@ -14,7 +14,11 @@ class C {
 
 //// [numericIndexerConstraint3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/numericIndexerConstraint4.js b/tests/baselines/reference/numericIndexerConstraint4.js
index 0f82789285d..8958392fe78 100644
--- a/tests/baselines/reference/numericIndexerConstraint4.js
+++ b/tests/baselines/reference/numericIndexerConstraint4.js
@@ -14,7 +14,11 @@ var x: {
 
 //// [numericIndexerConstraint4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/numericIndexerTyping2.js b/tests/baselines/reference/numericIndexerTyping2.js
index 1086d974590..5ce85e4c5eb 100644
--- a/tests/baselines/reference/numericIndexerTyping2.js
+++ b/tests/baselines/reference/numericIndexerTyping2.js
@@ -14,7 +14,11 @@ var r2: string = i2[1]; // error: numeric indexer returns the type of the string
 
 //// [numericIndexerTyping2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectCreationOfElementAccessExpression.js b/tests/baselines/reference/objectCreationOfElementAccessExpression.js
index 2b7ac176c7e..3f251e47029 100644
--- a/tests/baselines/reference/objectCreationOfElementAccessExpression.js
+++ b/tests/baselines/reference/objectCreationOfElementAccessExpression.js
@@ -57,7 +57,11 @@ var foods2: MonsterFood[] = new PetFood[new IceCream('Mint chocolate chip') , Co
 
 //// [objectCreationOfElementAccessExpression.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypeHidingMembersOfExtendedObject.js b/tests/baselines/reference/objectTypeHidingMembersOfExtendedObject.js
index 301761c2849..05dfd4bc818 100644
--- a/tests/baselines/reference/objectTypeHidingMembersOfExtendedObject.js
+++ b/tests/baselines/reference/objectTypeHidingMembersOfExtendedObject.js
@@ -56,7 +56,11 @@ var r4: void = b.valueOf();
 
 //// [objectTypeHidingMembersOfExtendedObject.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithNumericIndexers1.js b/tests/baselines/reference/objectTypesIdentityWithNumericIndexers1.js
index 1b889269724..9518317f230 100644
--- a/tests/baselines/reference/objectTypesIdentityWithNumericIndexers1.js
+++ b/tests/baselines/reference/objectTypesIdentityWithNumericIndexers1.js
@@ -125,7 +125,11 @@ function foo16(x: any) { }
 //// [objectTypesIdentityWithNumericIndexers1.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithNumericIndexers2.js b/tests/baselines/reference/objectTypesIdentityWithNumericIndexers2.js
index 767f10adc88..a5b93a32853 100644
--- a/tests/baselines/reference/objectTypesIdentityWithNumericIndexers2.js
+++ b/tests/baselines/reference/objectTypesIdentityWithNumericIndexers2.js
@@ -128,7 +128,11 @@ function foo16(x: any) { }
 //// [objectTypesIdentityWithNumericIndexers2.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithNumericIndexers3.js b/tests/baselines/reference/objectTypesIdentityWithNumericIndexers3.js
index 8ae7b92b4dd..14a70059adc 100644
--- a/tests/baselines/reference/objectTypesIdentityWithNumericIndexers3.js
+++ b/tests/baselines/reference/objectTypesIdentityWithNumericIndexers3.js
@@ -125,7 +125,11 @@ function foo16(x: any) { }
 //// [objectTypesIdentityWithNumericIndexers3.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithPrivates.js b/tests/baselines/reference/objectTypesIdentityWithPrivates.js
index 9f9319a3cf8..0d3ebae0bb8 100644
--- a/tests/baselines/reference/objectTypesIdentityWithPrivates.js
+++ b/tests/baselines/reference/objectTypesIdentityWithPrivates.js
@@ -123,7 +123,11 @@ function foo16(x: any) { }
 //// [objectTypesIdentityWithPrivates.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithPrivates2.js b/tests/baselines/reference/objectTypesIdentityWithPrivates2.js
index e1426e4a3b5..4fa90889d81 100644
--- a/tests/baselines/reference/objectTypesIdentityWithPrivates2.js
+++ b/tests/baselines/reference/objectTypesIdentityWithPrivates2.js
@@ -41,7 +41,11 @@ function foo6(x: any): any { }
 //// [objectTypesIdentityWithPrivates2.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithPrivates3.js b/tests/baselines/reference/objectTypesIdentityWithPrivates3.js
index 1105c06c204..6ca413637f5 100644
--- a/tests/baselines/reference/objectTypesIdentityWithPrivates3.js
+++ b/tests/baselines/reference/objectTypesIdentityWithPrivates3.js
@@ -27,7 +27,11 @@ var c3: C3<T2>;
 
 //// [objectTypesIdentityWithPrivates3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithStringIndexers.js b/tests/baselines/reference/objectTypesIdentityWithStringIndexers.js
index 9f076b52c60..6758afd5cb3 100644
--- a/tests/baselines/reference/objectTypesIdentityWithStringIndexers.js
+++ b/tests/baselines/reference/objectTypesIdentityWithStringIndexers.js
@@ -125,7 +125,11 @@ function foo16(x: any) { }
 //// [objectTypesIdentityWithStringIndexers.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/objectTypesIdentityWithStringIndexers2.js b/tests/baselines/reference/objectTypesIdentityWithStringIndexers2.js
index 75ad2243fe3..370c71533fb 100644
--- a/tests/baselines/reference/objectTypesIdentityWithStringIndexers2.js
+++ b/tests/baselines/reference/objectTypesIdentityWithStringIndexers2.js
@@ -128,7 +128,11 @@ function foo16(x: any) { }
 //// [objectTypesIdentityWithStringIndexers2.js]
 // object types are identical structurally
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/optionalConstructorArgInSuper.js b/tests/baselines/reference/optionalConstructorArgInSuper.js
index 4ebc1226146..e13ea6a702d 100644
--- a/tests/baselines/reference/optionalConstructorArgInSuper.js
+++ b/tests/baselines/reference/optionalConstructorArgInSuper.js
@@ -12,7 +12,11 @@ d2.foo();
 
 //// [optionalConstructorArgInSuper.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/optionalMethods.js b/tests/baselines/reference/optionalMethods.js
index 5cbd798ec89..b0af91c92f8 100644
--- a/tests/baselines/reference/optionalMethods.js
+++ b/tests/baselines/reference/optionalMethods.js
@@ -59,7 +59,11 @@ class Derived extends Base {
 
 //// [optionalMethods.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/optionalParamArgsTest.js b/tests/baselines/reference/optionalParamArgsTest.js
index 23ab5150579..91507916a55 100644
--- a/tests/baselines/reference/optionalParamArgsTest.js
+++ b/tests/baselines/reference/optionalParamArgsTest.js
@@ -126,7 +126,11 @@ fnOpt2(1, [2, 3], [1], true);
 //// [optionalParamArgsTest.js]
 // Optional parameter and default argument tests
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/optionalParamInOverride.js b/tests/baselines/reference/optionalParamInOverride.js
index 9d318cd9ae5..bc60d2507b0 100644
--- a/tests/baselines/reference/optionalParamInOverride.js
+++ b/tests/baselines/reference/optionalParamInOverride.js
@@ -9,7 +9,11 @@ class Y extends Z {
 
 //// [optionalParamInOverride.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/optionalParameterProperty.js b/tests/baselines/reference/optionalParameterProperty.js
index 3203c4e2e09..62058c1ecb3 100644
--- a/tests/baselines/reference/optionalParameterProperty.js
+++ b/tests/baselines/reference/optionalParameterProperty.js
@@ -13,7 +13,11 @@ class D extends C {
 
 //// [optionalParameterProperty.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/outModuleConcatAmd.js b/tests/baselines/reference/outModuleConcatAmd.js
index cab6be31d07..8a28677dbbf 100644
--- a/tests/baselines/reference/outModuleConcatAmd.js
+++ b/tests/baselines/reference/outModuleConcatAmd.js
@@ -10,7 +10,11 @@ export class B extends A { }
 
 //// [all.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/outModuleConcatAmd.js.map b/tests/baselines/reference/outModuleConcatAmd.js.map
index 9187aca0646..937bec93969 100644
--- a/tests/baselines/reference/outModuleConcatAmd.js.map
+++ b/tests/baselines/reference/outModuleConcatAmd.js.map
@@ -1,2 +1,2 @@
 //// [all.js.map]
-{"version":3,"file":"all.js","sourceRoot":"","sources":["tests/cases/compiler/ref/a.ts","tests/cases/compiler/b.ts"],"names":[],"mappings":";;;;;;;IACA;QAAA;QAAiB,CAAC;QAAD,QAAC;IAAD,CAAC,AAAlB,IAAkB;IAAL,cAAC;;;;ICAd;QAAuB,qBAAC;QAAxB;;QAA2B,CAAC;QAAD,QAAC;IAAD,CAAC,AAA5B,CAAuB,KAAC,GAAI;IAAf,cAAC"}
\ No newline at end of file
+{"version":3,"file":"all.js","sourceRoot":"","sources":["tests/cases/compiler/ref/a.ts","tests/cases/compiler/b.ts"],"names":[],"mappings":";;;;;;;;;;;IACA;QAAA;QAAiB,CAAC;QAAD,QAAC;IAAD,CAAC,AAAlB,IAAkB;IAAL,cAAC;;;;ICAd;QAAuB,qBAAC;QAAxB;;QAA2B,CAAC;QAAD,QAAC;IAAD,CAAC,AAA5B,CAAuB,KAAC,GAAI;IAAf,cAAC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/outModuleConcatAmd.sourcemap.txt b/tests/baselines/reference/outModuleConcatAmd.sourcemap.txt
index f07a95163f6..75af3bb54ac 100644
--- a/tests/baselines/reference/outModuleConcatAmd.sourcemap.txt
+++ b/tests/baselines/reference/outModuleConcatAmd.sourcemap.txt
@@ -9,7 +9,11 @@ emittedFile:all.js
 sourceFile:tests/cases/compiler/ref/a.ts
 -------------------------------------------------------------------
 >>>var __extends = (this && this.__extends) || function (d, b) {
->>>    Object.setPrototypeOf(d, b);
+>>>    if (typeof Object.setPrototypeOf === "function") {
+>>>        Object.setPrototypeOf(d, b);
+>>>    } else {
+>>>        d.__proto__ = b;
+>>>    }
 >>>    function __() { this.constructor = d; }
 >>>    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 >>>};
@@ -20,13 +24,13 @@ sourceFile:tests/cases/compiler/ref/a.ts
 2 >    ^^^^^^^^^^^^^^^^^^^->
 1 >
   >
-1 >Emitted(8, 5) Source(2, 1) + SourceIndex(0)
+1 >Emitted(12, 5) Source(2, 1) + SourceIndex(0)
 ---
 >>>        function A() {
 1->^^^^^^^^
 2 >        ^^->
 1->
-1->Emitted(9, 9) Source(2, 1) + SourceIndex(0)
+1->Emitted(13, 9) Source(2, 1) + SourceIndex(0)
 ---
 >>>        }
 1->^^^^^^^^
@@ -34,16 +38,16 @@ sourceFile:tests/cases/compiler/ref/a.ts
 3 >         ^^^^^^^^^->
 1->export class A { 
 2 >        }
-1->Emitted(10, 9) Source(2, 18) + SourceIndex(0)
-2 >Emitted(10, 10) Source(2, 19) + SourceIndex(0)
+1->Emitted(14, 9) Source(2, 18) + SourceIndex(0)
+2 >Emitted(14, 10) Source(2, 19) + SourceIndex(0)
 ---
 >>>        return A;
 1->^^^^^^^^
 2 >        ^^^^^^^^
 1->
 2 >        }
-1->Emitted(11, 9) Source(2, 18) + SourceIndex(0)
-2 >Emitted(11, 17) Source(2, 19) + SourceIndex(0)
+1->Emitted(15, 9) Source(2, 18) + SourceIndex(0)
+2 >Emitted(15, 17) Source(2, 19) + SourceIndex(0)
 ---
 >>>    }());
 1 >^^^^
@@ -55,18 +59,18 @@ sourceFile:tests/cases/compiler/ref/a.ts
 2 >    }
 3 >     
 4 >     export class A { }
-1 >Emitted(12, 5) Source(2, 18) + SourceIndex(0)
-2 >Emitted(12, 6) Source(2, 19) + SourceIndex(0)
-3 >Emitted(12, 6) Source(2, 1) + SourceIndex(0)
-4 >Emitted(12, 10) Source(2, 19) + SourceIndex(0)
+1 >Emitted(16, 5) Source(2, 18) + SourceIndex(0)
+2 >Emitted(16, 6) Source(2, 19) + SourceIndex(0)
+3 >Emitted(16, 6) Source(2, 1) + SourceIndex(0)
+4 >Emitted(16, 10) Source(2, 19) + SourceIndex(0)
 ---
 >>>    exports.A = A;
 1->^^^^
 2 >    ^^^^^^^^^^^^^^
 1->
 2 >    A
-1->Emitted(13, 5) Source(2, 14) + SourceIndex(0)
-2 >Emitted(13, 19) Source(2, 15) + SourceIndex(0)
+1->Emitted(17, 5) Source(2, 14) + SourceIndex(0)
+2 >Emitted(17, 19) Source(2, 15) + SourceIndex(0)
 ---
 -------------------------------------------------------------------
 emittedFile:all.js
@@ -80,21 +84,21 @@ sourceFile:tests/cases/compiler/b.ts
 2 >    ^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >import {A} from "./ref/a";
   >
-1 >Emitted(17, 5) Source(2, 1) + SourceIndex(1)
+1 >Emitted(21, 5) Source(2, 1) + SourceIndex(1)
 ---
 >>>        __extends(B, _super);
 1->^^^^^^^^
 2 >        ^^^^^^^^^^^^^^^^^^^^^
 1->export class B extends 
 2 >        A
-1->Emitted(18, 9) Source(2, 24) + SourceIndex(1)
-2 >Emitted(18, 30) Source(2, 25) + SourceIndex(1)
+1->Emitted(22, 9) Source(2, 24) + SourceIndex(1)
+2 >Emitted(22, 30) Source(2, 25) + SourceIndex(1)
 ---
 >>>        function B() {
 1 >^^^^^^^^
 2 >        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
-1 >Emitted(19, 9) Source(2, 1) + SourceIndex(1)
+1 >Emitted(23, 9) Source(2, 1) + SourceIndex(1)
 ---
 >>>            return _super.apply(this, arguments) || this;
 >>>        }
@@ -103,16 +107,16 @@ sourceFile:tests/cases/compiler/b.ts
 3 >         ^^^^^^^^^->
 1->export class B extends A { 
 2 >        }
-1->Emitted(21, 9) Source(2, 28) + SourceIndex(1)
-2 >Emitted(21, 10) Source(2, 29) + SourceIndex(1)
+1->Emitted(25, 9) Source(2, 28) + SourceIndex(1)
+2 >Emitted(25, 10) Source(2, 29) + SourceIndex(1)
 ---
 >>>        return B;
 1->^^^^^^^^
 2 >        ^^^^^^^^
 1->
 2 >        }
-1->Emitted(22, 9) Source(2, 28) + SourceIndex(1)
-2 >Emitted(22, 17) Source(2, 29) + SourceIndex(1)
+1->Emitted(26, 9) Source(2, 28) + SourceIndex(1)
+2 >Emitted(26, 17) Source(2, 29) + SourceIndex(1)
 ---
 >>>    }(a_1.A));
 1 >^^^^
@@ -128,20 +132,20 @@ sourceFile:tests/cases/compiler/b.ts
 4 >     export class B extends 
 5 >      A
 6 >            { }
-1 >Emitted(23, 5) Source(2, 28) + SourceIndex(1)
-2 >Emitted(23, 6) Source(2, 29) + SourceIndex(1)
-3 >Emitted(23, 6) Source(2, 1) + SourceIndex(1)
-4 >Emitted(23, 7) Source(2, 24) + SourceIndex(1)
-5 >Emitted(23, 12) Source(2, 25) + SourceIndex(1)
-6 >Emitted(23, 15) Source(2, 29) + SourceIndex(1)
+1 >Emitted(27, 5) Source(2, 28) + SourceIndex(1)
+2 >Emitted(27, 6) Source(2, 29) + SourceIndex(1)
+3 >Emitted(27, 6) Source(2, 1) + SourceIndex(1)
+4 >Emitted(27, 7) Source(2, 24) + SourceIndex(1)
+5 >Emitted(27, 12) Source(2, 25) + SourceIndex(1)
+6 >Emitted(27, 15) Source(2, 29) + SourceIndex(1)
 ---
 >>>    exports.B = B;
 1->^^^^
 2 >    ^^^^^^^^^^^^^^
 1->
 2 >    B
-1->Emitted(24, 5) Source(2, 14) + SourceIndex(1)
-2 >Emitted(24, 19) Source(2, 15) + SourceIndex(1)
+1->Emitted(28, 5) Source(2, 14) + SourceIndex(1)
+2 >Emitted(28, 19) Source(2, 15) + SourceIndex(1)
 ---
 >>>});
 >>>//# sourceMappingURL=all.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/outModuleConcatSystem.js b/tests/baselines/reference/outModuleConcatSystem.js
index 6f6e1c3b366..4a7552bcde8 100644
--- a/tests/baselines/reference/outModuleConcatSystem.js
+++ b/tests/baselines/reference/outModuleConcatSystem.js
@@ -10,7 +10,11 @@ export class B extends A { }
 
 //// [all.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/outModuleConcatSystem.js.map b/tests/baselines/reference/outModuleConcatSystem.js.map
index ac8fb23d87c..275b47b1363 100644
--- a/tests/baselines/reference/outModuleConcatSystem.js.map
+++ b/tests/baselines/reference/outModuleConcatSystem.js.map
@@ -1,2 +1,2 @@
 //// [all.js.map]
-{"version":3,"file":"all.js","sourceRoot":"","sources":["tests/cases/compiler/ref/a.ts","tests/cases/compiler/b.ts"],"names":[],"mappings":";;;;;;;;;;;;YACA;gBAAA;gBAAiB,CAAC;gBAAD,QAAC;YAAD,CAAC,AAAlB,IAAkB;;QAClB,CAAC;;;;;;;;;;;;;;YCDD;gBAAuB,qBAAC;gBAAxB;;gBAA2B,CAAC;gBAAD,QAAC;YAAD,CAAC,AAA5B,CAAuB,KAAC,GAAI;;QAAA,CAAC"}
\ No newline at end of file
+{"version":3,"file":"all.js","sourceRoot":"","sources":["tests/cases/compiler/ref/a.ts","tests/cases/compiler/b.ts"],"names":[],"mappings":";;;;;;;;;;;;;;;;YACA;gBAAA;gBAAiB,CAAC;gBAAD,QAAC;YAAD,CAAC,AAAlB,IAAkB;;QAClB,CAAC;;;;;;;;;;;;;;YCDD;gBAAuB,qBAAC;gBAAxB;;gBAA2B,CAAC;gBAAD,QAAC;YAAD,CAAC,AAA5B,CAAuB,KAAC,GAAI;;QAAA,CAAC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/outModuleConcatSystem.sourcemap.txt b/tests/baselines/reference/outModuleConcatSystem.sourcemap.txt
index 47558a3812a..e5a439aea1a 100644
--- a/tests/baselines/reference/outModuleConcatSystem.sourcemap.txt
+++ b/tests/baselines/reference/outModuleConcatSystem.sourcemap.txt
@@ -9,7 +9,11 @@ emittedFile:all.js
 sourceFile:tests/cases/compiler/ref/a.ts
 -------------------------------------------------------------------
 >>>var __extends = (this && this.__extends) || function (d, b) {
->>>    Object.setPrototypeOf(d, b);
+>>>    if (typeof Object.setPrototypeOf === "function") {
+>>>        Object.setPrototypeOf(d, b);
+>>>    } else {
+>>>        d.__proto__ = b;
+>>>    }
 >>>    function __() { this.constructor = d; }
 >>>    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 >>>};
@@ -25,13 +29,13 @@ sourceFile:tests/cases/compiler/ref/a.ts
 2 >            ^^^^^^^^^^^^^^^^^^^->
 1 >
   >
-1 >Emitted(13, 13) Source(2, 1) + SourceIndex(0)
+1 >Emitted(17, 13) Source(2, 1) + SourceIndex(0)
 ---
 >>>                function A() {
 1->^^^^^^^^^^^^^^^^
 2 >                ^^->
 1->
-1->Emitted(14, 17) Source(2, 1) + SourceIndex(0)
+1->Emitted(18, 17) Source(2, 1) + SourceIndex(0)
 ---
 >>>                }
 1->^^^^^^^^^^^^^^^^
@@ -39,16 +43,16 @@ sourceFile:tests/cases/compiler/ref/a.ts
 3 >                 ^^^^^^^^^->
 1->export class A { 
 2 >                }
-1->Emitted(15, 17) Source(2, 18) + SourceIndex(0)
-2 >Emitted(15, 18) Source(2, 19) + SourceIndex(0)
+1->Emitted(19, 17) Source(2, 18) + SourceIndex(0)
+2 >Emitted(19, 18) Source(2, 19) + SourceIndex(0)
 ---
 >>>                return A;
 1->^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^
 1->
 2 >                }
-1->Emitted(16, 17) Source(2, 18) + SourceIndex(0)
-2 >Emitted(16, 25) Source(2, 19) + SourceIndex(0)
+1->Emitted(20, 17) Source(2, 18) + SourceIndex(0)
+2 >Emitted(20, 25) Source(2, 19) + SourceIndex(0)
 ---
 >>>            }());
 1 >^^^^^^^^^^^^
@@ -60,10 +64,10 @@ sourceFile:tests/cases/compiler/ref/a.ts
 2 >            }
 3 >             
 4 >             export class A { }
-1 >Emitted(17, 13) Source(2, 18) + SourceIndex(0)
-2 >Emitted(17, 14) Source(2, 19) + SourceIndex(0)
-3 >Emitted(17, 14) Source(2, 1) + SourceIndex(0)
-4 >Emitted(17, 18) Source(2, 19) + SourceIndex(0)
+1 >Emitted(21, 13) Source(2, 18) + SourceIndex(0)
+2 >Emitted(21, 14) Source(2, 19) + SourceIndex(0)
+3 >Emitted(21, 14) Source(2, 1) + SourceIndex(0)
+4 >Emitted(21, 18) Source(2, 19) + SourceIndex(0)
 ---
 >>>            exports_1("A", A);
 >>>        }
@@ -72,8 +76,8 @@ sourceFile:tests/cases/compiler/ref/a.ts
 1->
   >
 2 >        
-1->Emitted(19, 9) Source(3, 1) + SourceIndex(0)
-2 >Emitted(19, 10) Source(3, 2) + SourceIndex(0)
+1->Emitted(23, 9) Source(3, 1) + SourceIndex(0)
+2 >Emitted(23, 10) Source(3, 2) + SourceIndex(0)
 ---
 -------------------------------------------------------------------
 emittedFile:all.js
@@ -97,21 +101,21 @@ sourceFile:tests/cases/compiler/b.ts
 2 >            ^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >import {A} from "./ref/a";
   >
-1 >Emitted(33, 13) Source(2, 1) + SourceIndex(1)
+1 >Emitted(37, 13) Source(2, 1) + SourceIndex(1)
 ---
 >>>                __extends(B, _super);
 1->^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^^^^^^^^^^^^^^
 1->export class B extends 
 2 >                A
-1->Emitted(34, 17) Source(2, 24) + SourceIndex(1)
-2 >Emitted(34, 38) Source(2, 25) + SourceIndex(1)
+1->Emitted(38, 17) Source(2, 24) + SourceIndex(1)
+2 >Emitted(38, 38) Source(2, 25) + SourceIndex(1)
 ---
 >>>                function B() {
 1 >^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
-1 >Emitted(35, 17) Source(2, 1) + SourceIndex(1)
+1 >Emitted(39, 17) Source(2, 1) + SourceIndex(1)
 ---
 >>>                    return _super.apply(this, arguments) || this;
 >>>                }
@@ -120,16 +124,16 @@ sourceFile:tests/cases/compiler/b.ts
 3 >                 ^^^^^^^^^->
 1->export class B extends A { 
 2 >                }
-1->Emitted(37, 17) Source(2, 28) + SourceIndex(1)
-2 >Emitted(37, 18) Source(2, 29) + SourceIndex(1)
+1->Emitted(41, 17) Source(2, 28) + SourceIndex(1)
+2 >Emitted(41, 18) Source(2, 29) + SourceIndex(1)
 ---
 >>>                return B;
 1->^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^
 1->
 2 >                }
-1->Emitted(38, 17) Source(2, 28) + SourceIndex(1)
-2 >Emitted(38, 25) Source(2, 29) + SourceIndex(1)
+1->Emitted(42, 17) Source(2, 28) + SourceIndex(1)
+2 >Emitted(42, 25) Source(2, 29) + SourceIndex(1)
 ---
 >>>            }(a_1.A));
 1 >^^^^^^^^^^^^
@@ -145,12 +149,12 @@ sourceFile:tests/cases/compiler/b.ts
 4 >             export class B extends 
 5 >              A
 6 >                    { }
-1 >Emitted(39, 13) Source(2, 28) + SourceIndex(1)
-2 >Emitted(39, 14) Source(2, 29) + SourceIndex(1)
-3 >Emitted(39, 14) Source(2, 1) + SourceIndex(1)
-4 >Emitted(39, 15) Source(2, 24) + SourceIndex(1)
-5 >Emitted(39, 20) Source(2, 25) + SourceIndex(1)
-6 >Emitted(39, 23) Source(2, 29) + SourceIndex(1)
+1 >Emitted(43, 13) Source(2, 28) + SourceIndex(1)
+2 >Emitted(43, 14) Source(2, 29) + SourceIndex(1)
+3 >Emitted(43, 14) Source(2, 1) + SourceIndex(1)
+4 >Emitted(43, 15) Source(2, 24) + SourceIndex(1)
+5 >Emitted(43, 20) Source(2, 25) + SourceIndex(1)
+6 >Emitted(43, 23) Source(2, 29) + SourceIndex(1)
 ---
 >>>            exports_2("B", B);
 >>>        }
@@ -158,8 +162,8 @@ sourceFile:tests/cases/compiler/b.ts
 2 >        ^
 1->
 2 >        
-1->Emitted(41, 9) Source(2, 29) + SourceIndex(1)
-2 >Emitted(41, 10) Source(2, 30) + SourceIndex(1)
+1->Emitted(45, 9) Source(2, 29) + SourceIndex(1)
+2 >Emitted(45, 10) Source(2, 30) + SourceIndex(1)
 ---
 >>>    };
 >>>});
diff --git a/tests/baselines/reference/outModuleTripleSlashRefs.js b/tests/baselines/reference/outModuleTripleSlashRefs.js
index 5f6def67a48..c5f6da0fdf5 100644
--- a/tests/baselines/reference/outModuleTripleSlashRefs.js
+++ b/tests/baselines/reference/outModuleTripleSlashRefs.js
@@ -32,7 +32,11 @@ export class B extends A { }
 
 //// [all.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/outModuleTripleSlashRefs.js.map b/tests/baselines/reference/outModuleTripleSlashRefs.js.map
index 5ccc59aeabf..cb10515edd2 100644
--- a/tests/baselines/reference/outModuleTripleSlashRefs.js.map
+++ b/tests/baselines/reference/outModuleTripleSlashRefs.js.map
@@ -1,2 +1,2 @@
 //// [all.js.map]
-{"version":3,"file":"all.js","sourceRoot":"","sources":["tests/cases/compiler/ref/b.ts","tests/cases/compiler/ref/a.ts","tests/cases/compiler/b.ts"],"names":[],"mappings":";;;;;AAAA,iCAAiC;AACjC;IAAA;IAEA,CAAC;IAAD,UAAC;AAAD,CAAC,AAFD,IAEC;;;ICFD,+BAA+B;IAC/B;QAAA;QAEA,CAAC;QAAD,QAAC;IAAD,CAAC,AAFD,IAEC;IAFY,cAAC;;;;ICDd;QAAuB,qBAAC;QAAxB;;QAA2B,CAAC;QAAD,QAAC;IAAD,CAAC,AAA5B,CAAuB,KAAC,GAAI;IAAf,cAAC"}
\ No newline at end of file
+{"version":3,"file":"all.js","sourceRoot":"","sources":["tests/cases/compiler/ref/b.ts","tests/cases/compiler/ref/a.ts","tests/cases/compiler/b.ts"],"names":[],"mappings":";;;;;;;;;AAAA,iCAAiC;AACjC;IAAA;IAEA,CAAC;IAAD,UAAC;AAAD,CAAC,AAFD,IAEC;;;ICFD,+BAA+B;IAC/B;QAAA;QAEA,CAAC;QAAD,QAAC;IAAD,CAAC,AAFD,IAEC;IAFY,cAAC;;;;ICDd;QAAuB,qBAAC;QAAxB;;QAA2B,CAAC;QAAD,QAAC;IAAD,CAAC,AAA5B,CAAuB,KAAC,GAAI;IAAf,cAAC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/outModuleTripleSlashRefs.sourcemap.txt b/tests/baselines/reference/outModuleTripleSlashRefs.sourcemap.txt
index 9f15bc0eaee..c3e619a4c2d 100644
--- a/tests/baselines/reference/outModuleTripleSlashRefs.sourcemap.txt
+++ b/tests/baselines/reference/outModuleTripleSlashRefs.sourcemap.txt
@@ -9,7 +9,11 @@ emittedFile:all.js
 sourceFile:tests/cases/compiler/ref/b.ts
 -------------------------------------------------------------------
 >>>var __extends = (this && this.__extends) || function (d, b) {
->>>    Object.setPrototypeOf(d, b);
+>>>    if (typeof Object.setPrototypeOf === "function") {
+>>>        Object.setPrototypeOf(d, b);
+>>>    } else {
+>>>        d.__proto__ = b;
+>>>    }
 >>>    function __() { this.constructor = d; }
 >>>    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 >>>};
@@ -18,21 +22,21 @@ sourceFile:tests/cases/compiler/ref/b.ts
 2 >^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 1 >
 2 >/// <reference path="./c.d.ts" />
-1 >Emitted(6, 1) Source(1, 1) + SourceIndex(0)
-2 >Emitted(6, 34) Source(1, 34) + SourceIndex(0)
+1 >Emitted(10, 1) Source(1, 1) + SourceIndex(0)
+2 >Emitted(10, 34) Source(1, 34) + SourceIndex(0)
 ---
 >>>var Foo = (function () {
 1 >
 2 >^^^^^^^^^^^^^^^^^^^^^->
 1 >
   >
-1 >Emitted(7, 1) Source(2, 1) + SourceIndex(0)
+1 >Emitted(11, 1) Source(2, 1) + SourceIndex(0)
 ---
 >>>    function Foo() {
 1->^^^^
 2 >    ^^->
 1->
-1->Emitted(8, 5) Source(2, 1) + SourceIndex(0)
+1->Emitted(12, 5) Source(2, 1) + SourceIndex(0)
 ---
 >>>    }
 1->^^^^
@@ -42,16 +46,16 @@ sourceFile:tests/cases/compiler/ref/b.ts
   >	member: Bar;
   >
 2 >    }
-1->Emitted(9, 5) Source(4, 1) + SourceIndex(0)
-2 >Emitted(9, 6) Source(4, 2) + SourceIndex(0)
+1->Emitted(13, 5) Source(4, 1) + SourceIndex(0)
+2 >Emitted(13, 6) Source(4, 2) + SourceIndex(0)
 ---
 >>>    return Foo;
 1->^^^^
 2 >    ^^^^^^^^^^
 1->
 2 >    }
-1->Emitted(10, 5) Source(4, 1) + SourceIndex(0)
-2 >Emitted(10, 15) Source(4, 2) + SourceIndex(0)
+1->Emitted(14, 5) Source(4, 1) + SourceIndex(0)
+2 >Emitted(14, 15) Source(4, 2) + SourceIndex(0)
 ---
 >>>}());
 1 >
@@ -65,10 +69,10 @@ sourceFile:tests/cases/compiler/ref/b.ts
 4 > class Foo {
   > 	member: Bar;
   > }
-1 >Emitted(11, 1) Source(4, 1) + SourceIndex(0)
-2 >Emitted(11, 2) Source(4, 2) + SourceIndex(0)
-3 >Emitted(11, 2) Source(2, 1) + SourceIndex(0)
-4 >Emitted(11, 6) Source(4, 2) + SourceIndex(0)
+1 >Emitted(15, 1) Source(4, 1) + SourceIndex(0)
+2 >Emitted(15, 2) Source(4, 2) + SourceIndex(0)
+3 >Emitted(15, 2) Source(2, 1) + SourceIndex(0)
+4 >Emitted(15, 6) Source(4, 2) + SourceIndex(0)
 ---
 -------------------------------------------------------------------
 emittedFile:all.js
@@ -82,21 +86,21 @@ sourceFile:tests/cases/compiler/ref/a.ts
 1->
   >
 2 >    /// <reference path="./b.ts" />
-1->Emitted(14, 5) Source(2, 1) + SourceIndex(1)
-2 >Emitted(14, 36) Source(2, 32) + SourceIndex(1)
+1->Emitted(18, 5) Source(2, 1) + SourceIndex(1)
+2 >Emitted(18, 36) Source(2, 32) + SourceIndex(1)
 ---
 >>>    var A = (function () {
 1 >^^^^
 2 >    ^^^^^^^^^^^^^^^^^^^->
 1 >
   >
-1 >Emitted(15, 5) Source(3, 1) + SourceIndex(1)
+1 >Emitted(19, 5) Source(3, 1) + SourceIndex(1)
 ---
 >>>        function A() {
 1->^^^^^^^^
 2 >        ^^->
 1->
-1->Emitted(16, 9) Source(3, 1) + SourceIndex(1)
+1->Emitted(20, 9) Source(3, 1) + SourceIndex(1)
 ---
 >>>        }
 1->^^^^^^^^
@@ -106,16 +110,16 @@ sourceFile:tests/cases/compiler/ref/a.ts
   >	member: typeof GlobalFoo;
   >
 2 >        }
-1->Emitted(17, 9) Source(5, 1) + SourceIndex(1)
-2 >Emitted(17, 10) Source(5, 2) + SourceIndex(1)
+1->Emitted(21, 9) Source(5, 1) + SourceIndex(1)
+2 >Emitted(21, 10) Source(5, 2) + SourceIndex(1)
 ---
 >>>        return A;
 1->^^^^^^^^
 2 >        ^^^^^^^^
 1->
 2 >        }
-1->Emitted(18, 9) Source(5, 1) + SourceIndex(1)
-2 >Emitted(18, 17) Source(5, 2) + SourceIndex(1)
+1->Emitted(22, 9) Source(5, 1) + SourceIndex(1)
+2 >Emitted(22, 17) Source(5, 2) + SourceIndex(1)
 ---
 >>>    }());
 1 >^^^^
@@ -129,18 +133,18 @@ sourceFile:tests/cases/compiler/ref/a.ts
 4 >     export class A {
   >     	member: typeof GlobalFoo;
   >     }
-1 >Emitted(19, 5) Source(5, 1) + SourceIndex(1)
-2 >Emitted(19, 6) Source(5, 2) + SourceIndex(1)
-3 >Emitted(19, 6) Source(3, 1) + SourceIndex(1)
-4 >Emitted(19, 10) Source(5, 2) + SourceIndex(1)
+1 >Emitted(23, 5) Source(5, 1) + SourceIndex(1)
+2 >Emitted(23, 6) Source(5, 2) + SourceIndex(1)
+3 >Emitted(23, 6) Source(3, 1) + SourceIndex(1)
+4 >Emitted(23, 10) Source(5, 2) + SourceIndex(1)
 ---
 >>>    exports.A = A;
 1->^^^^
 2 >    ^^^^^^^^^^^^^^
 1->
 2 >    A
-1->Emitted(20, 5) Source(3, 14) + SourceIndex(1)
-2 >Emitted(20, 19) Source(3, 15) + SourceIndex(1)
+1->Emitted(24, 5) Source(3, 14) + SourceIndex(1)
+2 >Emitted(24, 19) Source(3, 15) + SourceIndex(1)
 ---
 -------------------------------------------------------------------
 emittedFile:all.js
@@ -154,21 +158,21 @@ sourceFile:tests/cases/compiler/b.ts
 2 >    ^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >import {A} from "./ref/a";
   >
-1 >Emitted(24, 5) Source(2, 1) + SourceIndex(2)
+1 >Emitted(28, 5) Source(2, 1) + SourceIndex(2)
 ---
 >>>        __extends(B, _super);
 1->^^^^^^^^
 2 >        ^^^^^^^^^^^^^^^^^^^^^
 1->export class B extends 
 2 >        A
-1->Emitted(25, 9) Source(2, 24) + SourceIndex(2)
-2 >Emitted(25, 30) Source(2, 25) + SourceIndex(2)
+1->Emitted(29, 9) Source(2, 24) + SourceIndex(2)
+2 >Emitted(29, 30) Source(2, 25) + SourceIndex(2)
 ---
 >>>        function B() {
 1 >^^^^^^^^
 2 >        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
-1 >Emitted(26, 9) Source(2, 1) + SourceIndex(2)
+1 >Emitted(30, 9) Source(2, 1) + SourceIndex(2)
 ---
 >>>            return _super.apply(this, arguments) || this;
 >>>        }
@@ -177,16 +181,16 @@ sourceFile:tests/cases/compiler/b.ts
 3 >         ^^^^^^^^^->
 1->export class B extends A { 
 2 >        }
-1->Emitted(28, 9) Source(2, 28) + SourceIndex(2)
-2 >Emitted(28, 10) Source(2, 29) + SourceIndex(2)
+1->Emitted(32, 9) Source(2, 28) + SourceIndex(2)
+2 >Emitted(32, 10) Source(2, 29) + SourceIndex(2)
 ---
 >>>        return B;
 1->^^^^^^^^
 2 >        ^^^^^^^^
 1->
 2 >        }
-1->Emitted(29, 9) Source(2, 28) + SourceIndex(2)
-2 >Emitted(29, 17) Source(2, 29) + SourceIndex(2)
+1->Emitted(33, 9) Source(2, 28) + SourceIndex(2)
+2 >Emitted(33, 17) Source(2, 29) + SourceIndex(2)
 ---
 >>>    }(a_1.A));
 1 >^^^^
@@ -202,20 +206,20 @@ sourceFile:tests/cases/compiler/b.ts
 4 >     export class B extends 
 5 >      A
 6 >            { }
-1 >Emitted(30, 5) Source(2, 28) + SourceIndex(2)
-2 >Emitted(30, 6) Source(2, 29) + SourceIndex(2)
-3 >Emitted(30, 6) Source(2, 1) + SourceIndex(2)
-4 >Emitted(30, 7) Source(2, 24) + SourceIndex(2)
-5 >Emitted(30, 12) Source(2, 25) + SourceIndex(2)
-6 >Emitted(30, 15) Source(2, 29) + SourceIndex(2)
+1 >Emitted(34, 5) Source(2, 28) + SourceIndex(2)
+2 >Emitted(34, 6) Source(2, 29) + SourceIndex(2)
+3 >Emitted(34, 6) Source(2, 1) + SourceIndex(2)
+4 >Emitted(34, 7) Source(2, 24) + SourceIndex(2)
+5 >Emitted(34, 12) Source(2, 25) + SourceIndex(2)
+6 >Emitted(34, 15) Source(2, 29) + SourceIndex(2)
 ---
 >>>    exports.B = B;
 1->^^^^
 2 >    ^^^^^^^^^^^^^^
 1->
 2 >    B
-1->Emitted(31, 5) Source(2, 14) + SourceIndex(2)
-2 >Emitted(31, 19) Source(2, 15) + SourceIndex(2)
+1->Emitted(35, 5) Source(2, 14) + SourceIndex(2)
+2 >Emitted(35, 19) Source(2, 15) + SourceIndex(2)
 ---
 >>>});
 >>>//# sourceMappingURL=all.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/overload1.js b/tests/baselines/reference/overload1.js
index 6cbfb843812..8377a62f2c7 100644
--- a/tests/baselines/reference/overload1.js
+++ b/tests/baselines/reference/overload1.js
@@ -41,7 +41,11 @@ var v=x.g;
 
 //// [overload1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadOnConstConstraintChecks1.js b/tests/baselines/reference/overloadOnConstConstraintChecks1.js
index 8bc8ccd1612..ae8e1178be5 100644
--- a/tests/baselines/reference/overloadOnConstConstraintChecks1.js
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks1.js
@@ -24,7 +24,11 @@ class D implements MyDoc {
 
 //// [overloadOnConstConstraintChecks1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadOnConstConstraintChecks2.js b/tests/baselines/reference/overloadOnConstConstraintChecks2.js
index 16cfb630a5d..43468e15fd8 100644
--- a/tests/baselines/reference/overloadOnConstConstraintChecks2.js
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks2.js
@@ -13,7 +13,11 @@ function foo(name: any): A {
 
 //// [overloadOnConstConstraintChecks2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadOnConstConstraintChecks3.js b/tests/baselines/reference/overloadOnConstConstraintChecks3.js
index 1540bc4dc49..5e8d70d3d6e 100644
--- a/tests/baselines/reference/overloadOnConstConstraintChecks3.js
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks3.js
@@ -14,7 +14,11 @@ function foo(name: any): A {
 
 //// [overloadOnConstConstraintChecks3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadOnConstConstraintChecks4.js b/tests/baselines/reference/overloadOnConstConstraintChecks4.js
index a634547a36b..c4ac235a671 100644
--- a/tests/baselines/reference/overloadOnConstConstraintChecks4.js
+++ b/tests/baselines/reference/overloadOnConstConstraintChecks4.js
@@ -15,7 +15,11 @@ function foo(name: any): Z {
 
 //// [overloadOnConstConstraintChecks4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadOnConstantsInvalidOverload1.js b/tests/baselines/reference/overloadOnConstantsInvalidOverload1.js
index 0edadc3c692..58807808f5c 100644
--- a/tests/baselines/reference/overloadOnConstantsInvalidOverload1.js
+++ b/tests/baselines/reference/overloadOnConstantsInvalidOverload1.js
@@ -13,7 +13,11 @@ foo("HI");
 
 //// [overloadOnConstantsInvalidOverload1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadResolution.js b/tests/baselines/reference/overloadResolution.js
index 56ebebc454e..bb1fce13a0a 100644
--- a/tests/baselines/reference/overloadResolution.js
+++ b/tests/baselines/reference/overloadResolution.js
@@ -96,7 +96,11 @@ var s = fn5((n) => n.substr(0));
 
 //// [overloadResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadResolutionClassConstructors.js b/tests/baselines/reference/overloadResolutionClassConstructors.js
index 5cf41a3b44a..16bdd16eaa2 100644
--- a/tests/baselines/reference/overloadResolutionClassConstructors.js
+++ b/tests/baselines/reference/overloadResolutionClassConstructors.js
@@ -103,7 +103,11 @@ new fn5((n) => n.blah); // Error
 
 //// [overloadResolutionClassConstructors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadResolutionConstructors.js b/tests/baselines/reference/overloadResolutionConstructors.js
index 85ec9fb06fb..4b7e487466c 100644
--- a/tests/baselines/reference/overloadResolutionConstructors.js
+++ b/tests/baselines/reference/overloadResolutionConstructors.js
@@ -104,7 +104,11 @@ var s = new fn5((n) => n.substr(0));
 
 //// [overloadResolutionConstructors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadingOnConstants1.js b/tests/baselines/reference/overloadingOnConstants1.js
index c8f5a8fd9ae..d52d97cefc7 100644
--- a/tests/baselines/reference/overloadingOnConstants1.js
+++ b/tests/baselines/reference/overloadingOnConstants1.js
@@ -27,7 +27,11 @@ var htmlSpanElement2: Derived1 = d2.createElement("span");
 
 //// [overloadingOnConstants1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overloadingOnConstants2.js b/tests/baselines/reference/overloadingOnConstants2.js
index 9792485e1cf..3b666b2351b 100644
--- a/tests/baselines/reference/overloadingOnConstants2.js
+++ b/tests/baselines/reference/overloadingOnConstants2.js
@@ -29,7 +29,11 @@ var f: C = bar("um", []); // C
 
 //// [overloadingOnConstants2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/overridingPrivateStaticMembers.js b/tests/baselines/reference/overridingPrivateStaticMembers.js
index 50f957c7fdd..f1cc4b05a40 100644
--- a/tests/baselines/reference/overridingPrivateStaticMembers.js
+++ b/tests/baselines/reference/overridingPrivateStaticMembers.js
@@ -9,7 +9,11 @@ class Derived2 extends Base2 {
 
 //// [overridingPrivateStaticMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parseErrorInHeritageClause1.js b/tests/baselines/reference/parseErrorInHeritageClause1.js
index 3409c13e2f1..a82e4eb8ea7 100644
--- a/tests/baselines/reference/parseErrorInHeritageClause1.js
+++ b/tests/baselines/reference/parseErrorInHeritageClause1.js
@@ -4,7 +4,11 @@ class C extends A # {
 
 //// [parseErrorInHeritageClause1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parser509630.js b/tests/baselines/reference/parser509630.js
index cce7df3db54..3c80c2bfd16 100644
--- a/tests/baselines/reference/parser509630.js
+++ b/tests/baselines/reference/parser509630.js
@@ -8,7 +8,11 @@ class Any extends Type {
 
 //// [parser509630.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserAstSpans1.js b/tests/baselines/reference/parserAstSpans1.js
index 12de33e4738..5ba4ba4d96d 100644
--- a/tests/baselines/reference/parserAstSpans1.js
+++ b/tests/baselines/reference/parserAstSpans1.js
@@ -221,7 +221,11 @@ class c6 extends c5 {
 
 //// [parserAstSpans1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserClassDeclaration1.js b/tests/baselines/reference/parserClassDeclaration1.js
index 555d625d522..4ce80bdec21 100644
--- a/tests/baselines/reference/parserClassDeclaration1.js
+++ b/tests/baselines/reference/parserClassDeclaration1.js
@@ -4,7 +4,11 @@ class C extends A extends B {
 
 //// [parserClassDeclaration1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserClassDeclaration3.js b/tests/baselines/reference/parserClassDeclaration3.js
index b63483411b2..ac58fb23342 100644
--- a/tests/baselines/reference/parserClassDeclaration3.js
+++ b/tests/baselines/reference/parserClassDeclaration3.js
@@ -4,7 +4,11 @@ class C implements A extends B {
 
 //// [parserClassDeclaration3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserClassDeclaration4.js b/tests/baselines/reference/parserClassDeclaration4.js
index 2f3cdf0e166..fa85ee2659c 100644
--- a/tests/baselines/reference/parserClassDeclaration4.js
+++ b/tests/baselines/reference/parserClassDeclaration4.js
@@ -4,7 +4,11 @@ class C extends A implements B extends C {
 
 //// [parserClassDeclaration4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserClassDeclaration5.js b/tests/baselines/reference/parserClassDeclaration5.js
index da843d06292..a77e0867d59 100644
--- a/tests/baselines/reference/parserClassDeclaration5.js
+++ b/tests/baselines/reference/parserClassDeclaration5.js
@@ -4,7 +4,11 @@ class C extends A implements B implements C {
 
 //// [parserClassDeclaration5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserClassDeclaration6.js b/tests/baselines/reference/parserClassDeclaration6.js
index 842b811de9b..23820f706df 100644
--- a/tests/baselines/reference/parserClassDeclaration6.js
+++ b/tests/baselines/reference/parserClassDeclaration6.js
@@ -4,7 +4,11 @@ class C extends A, B {
 
 //// [parserClassDeclaration6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause2.js b/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause2.js
index 22225819435..d81e0e7cf65 100644
--- a/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause2.js
+++ b/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause2.js
@@ -4,7 +4,11 @@ class C extends A, {
 
 //// [parserErrorRecovery_ExtendsOrImplementsClause2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause4.js b/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause4.js
index 92af44f7cc4..34f0bce2d1c 100644
--- a/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause4.js
+++ b/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause4.js
@@ -4,7 +4,11 @@ class C extends A implements {
 
 //// [parserErrorRecovery_ExtendsOrImplementsClause4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause5.js b/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause5.js
index 07adb1e2001..9eb5a995637 100644
--- a/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause5.js
+++ b/tests/baselines/reference/parserErrorRecovery_ExtendsOrImplementsClause5.js
@@ -4,7 +4,11 @@ class C extends A, implements B, {
 
 //// [parserErrorRecovery_ExtendsOrImplementsClause5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserGenericsInTypeContexts1.js b/tests/baselines/reference/parserGenericsInTypeContexts1.js
index ef93433301b..99cfeb0c61f 100644
--- a/tests/baselines/reference/parserGenericsInTypeContexts1.js
+++ b/tests/baselines/reference/parserGenericsInTypeContexts1.js
@@ -19,7 +19,11 @@ function f2(): F<T> {
 
 //// [parserGenericsInTypeContexts1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserGenericsInTypeContexts2.js b/tests/baselines/reference/parserGenericsInTypeContexts2.js
index a3bfafc19b4..b34364d5b9e 100644
--- a/tests/baselines/reference/parserGenericsInTypeContexts2.js
+++ b/tests/baselines/reference/parserGenericsInTypeContexts2.js
@@ -19,7 +19,11 @@ function f2(): F<X<T>, Y<Z<T>>> {
 
 //// [parserGenericsInTypeContexts2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserRealSource10.js b/tests/baselines/reference/parserRealSource10.js
index b89e47d3e75..25112efe231 100644
--- a/tests/baselines/reference/parserRealSource10.js
+++ b/tests/baselines/reference/parserRealSource10.js
@@ -459,7 +459,11 @@ module TypeScript {
 // Copyright (c) Microsoft. All rights reserved. Licensed under the Apache License, Version 2.0. 
 // See LICENSE.txt in the project root for complete license information.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserRealSource11.js b/tests/baselines/reference/parserRealSource11.js
index daaa9f79cee..23ea8da3d5c 100644
--- a/tests/baselines/reference/parserRealSource11.js
+++ b/tests/baselines/reference/parserRealSource11.js
@@ -2368,7 +2368,11 @@ module TypeScript {
 // Copyright (c) Microsoft. All rights reserved. Licensed under the Apache License, Version 2.0. 
 // See LICENSE.txt in the project root for complete license information.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/parserharness.js b/tests/baselines/reference/parserharness.js
index fd432660b52..ac60a5b18ad 100644
--- a/tests/baselines/reference/parserharness.js
+++ b/tests/baselines/reference/parserharness.js
@@ -2097,7 +2097,11 @@ module Harness {
 // limitations under the License.
 //
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/partiallyAnnotatedFunctionInferenceError.js b/tests/baselines/reference/partiallyAnnotatedFunctionInferenceError.js
index c81647e79b5..b57b3a8bff6 100644
--- a/tests/baselines/reference/partiallyAnnotatedFunctionInferenceError.js
+++ b/tests/baselines/reference/partiallyAnnotatedFunctionInferenceError.js
@@ -17,7 +17,11 @@ testError((t1, t2, t3: D) => {})
 
 //// [partiallyAnnotatedFunctionInferenceError.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/partiallyAnnotatedFunctionInferenceWithTypeParameter.js b/tests/baselines/reference/partiallyAnnotatedFunctionInferenceWithTypeParameter.js
index e54441df4d6..f8bd04cde38 100644
--- a/tests/baselines/reference/partiallyAnnotatedFunctionInferenceWithTypeParameter.js
+++ b/tests/baselines/reference/partiallyAnnotatedFunctionInferenceWithTypeParameter.js
@@ -36,7 +36,11 @@ testRest((t2, ...t3: D[]) => {})
 
 //// [partiallyAnnotatedFunctionInferenceWithTypeParameter.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/primitiveMembers.js b/tests/baselines/reference/primitiveMembers.js
index 64b699496bf..2aa2efbba10 100644
--- a/tests/baselines/reference/primitiveMembers.js
+++ b/tests/baselines/reference/primitiveMembers.js
@@ -33,7 +33,11 @@ class foo extends baz { public bar(){ return undefined}; }
 
 //// [primitiveMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privacyClass.js b/tests/baselines/reference/privacyClass.js
index 64e1c63eca1..c310bf6e77d 100644
--- a/tests/baselines/reference/privacyClass.js
+++ b/tests/baselines/reference/privacyClass.js
@@ -130,7 +130,11 @@ export class glo_C12_public extends glo_c_private implements  glo_i_private, glo
 //// [privacyClass.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privacyClassExtendsClauseDeclFile.js b/tests/baselines/reference/privacyClassExtendsClauseDeclFile.js
index 377b4082bea..68feed955d3 100644
--- a/tests/baselines/reference/privacyClassExtendsClauseDeclFile.js
+++ b/tests/baselines/reference/privacyClassExtendsClauseDeclFile.js
@@ -100,7 +100,11 @@ class publicClassExtendingPublicClassInGlobal extends publicClassInGlobal {
 //// [privacyClassExtendsClauseDeclFile_externalModule.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -286,7 +290,11 @@ var publicClassExtendingFromPrivateModuleClass = (function (_super) {
 exports.publicClassExtendingFromPrivateModuleClass = publicClassExtendingFromPrivateModuleClass;
 //// [privacyClassExtendsClauseDeclFile_GlobalFile.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privacyGloClass.js b/tests/baselines/reference/privacyGloClass.js
index b93ed51025d..4824da462ad 100644
--- a/tests/baselines/reference/privacyGloClass.js
+++ b/tests/baselines/reference/privacyGloClass.js
@@ -62,7 +62,11 @@ class glo_C11_public extends glo_c_public implements glo_i_public {
 
 //// [privacyGloClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privateAccessInSubclass1.js b/tests/baselines/reference/privateAccessInSubclass1.js
index 2118eb072d7..63e8172576a 100644
--- a/tests/baselines/reference/privateAccessInSubclass1.js
+++ b/tests/baselines/reference/privateAccessInSubclass1.js
@@ -11,7 +11,11 @@ class D extends Base {
 
 //// [privateAccessInSubclass1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privateInstanceMemberAccessibility.js b/tests/baselines/reference/privateInstanceMemberAccessibility.js
index 98b2671d23e..3df2708569c 100644
--- a/tests/baselines/reference/privateInstanceMemberAccessibility.js
+++ b/tests/baselines/reference/privateInstanceMemberAccessibility.js
@@ -15,7 +15,11 @@ class Derived extends Base {
 
 //// [privateInstanceMemberAccessibility.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privateProtectedMembersAreNotAccessibleDestructuring.js b/tests/baselines/reference/privateProtectedMembersAreNotAccessibleDestructuring.js
index bcef17bf63f..239d0a4281b 100644
--- a/tests/baselines/reference/privateProtectedMembersAreNotAccessibleDestructuring.js
+++ b/tests/baselines/reference/privateProtectedMembersAreNotAccessibleDestructuring.js
@@ -23,7 +23,11 @@ let { priv: a, prot: b, privateMethod: f } = k; // error
 
 //// [privateProtectedMembersAreNotAccessibleDestructuring.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privateStaticMemberAccessibility.js b/tests/baselines/reference/privateStaticMemberAccessibility.js
index 438f485e031..d21d13070d8 100644
--- a/tests/baselines/reference/privateStaticMemberAccessibility.js
+++ b/tests/baselines/reference/privateStaticMemberAccessibility.js
@@ -10,7 +10,11 @@ class Derived extends Base {
 
 //// [privateStaticMemberAccessibility.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/privateStaticNotAccessibleInClodule2.js b/tests/baselines/reference/privateStaticNotAccessibleInClodule2.js
index 618d6d88e8a..e7e1e468aed 100644
--- a/tests/baselines/reference/privateStaticNotAccessibleInClodule2.js
+++ b/tests/baselines/reference/privateStaticNotAccessibleInClodule2.js
@@ -17,7 +17,11 @@ module D {
 //// [privateStaticNotAccessibleInClodule2.js]
 // Any attempt to access a private property member outside the class body that contains its declaration results in a compile-time error.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/amd/testGlo.js b/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/amd/testGlo.js
index ef754cba47d..93d8685224b 100644
--- a/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/amd/testGlo.js
+++ b/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/amd/testGlo.js
@@ -1,5 +1,9 @@
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/node/testGlo.js b/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/node/testGlo.js
index ef754cba47d..93d8685224b 100644
--- a/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/node/testGlo.js
+++ b/tests/baselines/reference/project/privacyCheckOnImportedModuleDeclarationsInsideModule/node/testGlo.js
@@ -1,5 +1,9 @@
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/project/prologueEmit/amd/out.js b/tests/baselines/reference/project/prologueEmit/amd/out.js
index 8273c054fbd..f80f316d3c8 100644
--- a/tests/baselines/reference/project/prologueEmit/amd/out.js
+++ b/tests/baselines/reference/project/prologueEmit/amd/out.js
@@ -1,5 +1,9 @@
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/project/prologueEmit/node/out.js b/tests/baselines/reference/project/prologueEmit/node/out.js
index 8273c054fbd..f80f316d3c8 100644
--- a/tests/baselines/reference/project/prologueEmit/node/out.js
+++ b/tests/baselines/reference/project/prologueEmit/node/out.js
@@ -1,5 +1,9 @@
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/project/quotesInFileAndDirectoryNames/amd/m'ain.js b/tests/baselines/reference/project/quotesInFileAndDirectoryNames/amd/m'ain.js
index dac535093f5..65483bd492a 100644
--- a/tests/baselines/reference/project/quotesInFileAndDirectoryNames/amd/m'ain.js
+++ b/tests/baselines/reference/project/quotesInFileAndDirectoryNames/amd/m'ain.js
@@ -1,6 +1,10 @@
 /// <reference path="li'b/class'A.ts" />
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/project/quotesInFileAndDirectoryNames/node/m'ain.js b/tests/baselines/reference/project/quotesInFileAndDirectoryNames/node/m'ain.js
index dac535093f5..65483bd492a 100644
--- a/tests/baselines/reference/project/quotesInFileAndDirectoryNames/node/m'ain.js
+++ b/tests/baselines/reference/project/quotesInFileAndDirectoryNames/node/m'ain.js
@@ -1,6 +1,10 @@
 /// <reference path="li'b/class'A.ts" />
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/propertiesAndIndexers.js b/tests/baselines/reference/propertiesAndIndexers.js
index ccf7c50ebc9..9d65b48702e 100644
--- a/tests/baselines/reference/propertiesAndIndexers.js
+++ b/tests/baselines/reference/propertiesAndIndexers.js
@@ -53,7 +53,11 @@ var c: {
 
 //// [propertiesAndIndexers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/propertyAccess.js b/tests/baselines/reference/propertyAccess.js
index 3240f46a935..3da9b5cc647 100644
--- a/tests/baselines/reference/propertyAccess.js
+++ b/tests/baselines/reference/propertyAccess.js
@@ -152,7 +152,11 @@ var x3: A;
 
 //// [propertyAccess.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints2.js b/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints2.js
index e813239484b..cc874197c3c 100644
--- a/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints2.js
+++ b/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints2.js
@@ -84,7 +84,11 @@ var r4 = b.foo(aB, aB); // no inferences for T so constraint isn't satisfied, er
 //// [propertyAccessOnTypeParameterWithConstraints2.js]
 // generic types should behave as if they have properties of their constraint type
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints3.js b/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints3.js
index b10642c73c5..bcaa1458325 100644
--- a/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints3.js
+++ b/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints3.js
@@ -59,7 +59,11 @@ var r4 = b.foo(new B()); // valid call to an invalid function
 //// [propertyAccessOnTypeParameterWithConstraints3.js]
 // generic types should behave as if they have properties of their constraint type
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints5.js b/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints5.js
index 97f8e18f917..8cc85faa100 100644
--- a/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints5.js
+++ b/tests/baselines/reference/propertyAccessOnTypeParameterWithConstraints5.js
@@ -46,7 +46,11 @@ var r4 = b.foo(new B()); // error after constraints above made illegal, doesn't
 
 //// [propertyAccessOnTypeParameterWithConstraints5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass.js b/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass.js
index 226ad97f81f..babef969a10 100644
--- a/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass.js
+++ b/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass.js
@@ -40,7 +40,11 @@ class E extends C {
 
 //// [protectedClassPropertyAccessibleWithinNestedSubclass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass1.js b/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass1.js
index c98abd2a89a..3a3013d6704 100644
--- a/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass1.js
+++ b/tests/baselines/reference/protectedClassPropertyAccessibleWithinNestedSubclass1.js
@@ -116,7 +116,11 @@ d4.x;                   // Error, neither within their declaring class nor class
 
 //// [protectedClassPropertyAccessibleWithinNestedSubclass1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass.js b/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass.js
index 2557a8abcf9..3c59a316d71 100644
--- a/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass.js
+++ b/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass.js
@@ -22,7 +22,11 @@ class C extends B {
 //// [protectedClassPropertyAccessibleWithinSubclass.js]
 // no errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass2.js b/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass2.js
index 8ee957ec64f..fb818c42c7e 100644
--- a/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass2.js
+++ b/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass2.js
@@ -96,7 +96,11 @@ d4.x;                   // Error, neither within their declaring class nor class
 
 //// [protectedClassPropertyAccessibleWithinSubclass2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass3.js b/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass3.js
index 31c2f3d149c..20984b107b9 100644
--- a/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass3.js
+++ b/tests/baselines/reference/protectedClassPropertyAccessibleWithinSubclass3.js
@@ -15,7 +15,11 @@ class Derived extends Base {
 
 //// [protectedClassPropertyAccessibleWithinSubclass3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedInstanceMemberAccessibility.js b/tests/baselines/reference/protectedInstanceMemberAccessibility.js
index 84400a37aa7..c906f456d67 100644
--- a/tests/baselines/reference/protectedInstanceMemberAccessibility.js
+++ b/tests/baselines/reference/protectedInstanceMemberAccessibility.js
@@ -46,7 +46,11 @@ class C extends A {
 
 //// [protectedInstanceMemberAccessibility.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedMembers.js b/tests/baselines/reference/protectedMembers.js
index 4757f6134a3..d2e8bfe47ce 100644
--- a/tests/baselines/reference/protectedMembers.js
+++ b/tests/baselines/reference/protectedMembers.js
@@ -117,7 +117,11 @@ class B3 extends A3 {
 
 //// [protectedMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass.js b/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass.js
index ffe163716ed..e0ad17934c3 100644
--- a/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass.js
+++ b/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass.js
@@ -45,7 +45,11 @@ Derived3.x;     // Error, neither within their declaring class nor classes deriv
 
 //// [protectedStaticClassPropertyAccessibleWithinSubclass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass2.js b/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass2.js
index d21e6511c34..37ddb2b0d2c 100644
--- a/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass2.js
+++ b/tests/baselines/reference/protectedStaticClassPropertyAccessibleWithinSubclass2.js
@@ -23,7 +23,11 @@ class Derived2 extends Derived1 {
 
 //// [protectedStaticClassPropertyAccessibleWithinSubclass2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/qualifiedName_entity-name-resolution-does-not-affect-class-heritage.js b/tests/baselines/reference/qualifiedName_entity-name-resolution-does-not-affect-class-heritage.js
index d345bb7e1b1..3fc3b29ff45 100644
--- a/tests/baselines/reference/qualifiedName_entity-name-resolution-does-not-affect-class-heritage.js
+++ b/tests/baselines/reference/qualifiedName_entity-name-resolution-does-not-affect-class-heritage.js
@@ -8,7 +8,11 @@ class Beta extends Alpha.x {
 
 //// [qualifiedName_entity-name-resolution-does-not-affect-class-heritage.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/readonlyConstructorAssignment.js b/tests/baselines/reference/readonlyConstructorAssignment.js
index d8275690d4a..a3a46c4e14f 100644
--- a/tests/baselines/reference/readonlyConstructorAssignment.js
+++ b/tests/baselines/reference/readonlyConstructorAssignment.js
@@ -42,7 +42,11 @@ class E extends D {
 //// [readonlyConstructorAssignment.js]
 // Tests that readonly parameter properties behave like regular readonly properties
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveBaseCheck3.js b/tests/baselines/reference/recursiveBaseCheck3.js
index 92835b848ce..bd89b8c6574 100644
--- a/tests/baselines/reference/recursiveBaseCheck3.js
+++ b/tests/baselines/reference/recursiveBaseCheck3.js
@@ -6,7 +6,11 @@ class C<T> extends A<T> { }
 
 //// [recursiveBaseCheck3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveBaseCheck4.js b/tests/baselines/reference/recursiveBaseCheck4.js
index f0271b2d36a..f89b52e719f 100644
--- a/tests/baselines/reference/recursiveBaseCheck4.js
+++ b/tests/baselines/reference/recursiveBaseCheck4.js
@@ -4,7 +4,11 @@ class M<T> extends M<string> { }
 
 //// [recursiveBaseCheck4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveBaseCheck6.js b/tests/baselines/reference/recursiveBaseCheck6.js
index 97e6cb483e3..05a72e11213 100644
--- a/tests/baselines/reference/recursiveBaseCheck6.js
+++ b/tests/baselines/reference/recursiveBaseCheck6.js
@@ -4,7 +4,11 @@ class S18<A> extends S18<{ S19: A; }>{ }
 
 //// [recursiveBaseCheck6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveBaseConstructorCreation1.js b/tests/baselines/reference/recursiveBaseConstructorCreation1.js
index d20d43c405d..b0a11841dd8 100644
--- a/tests/baselines/reference/recursiveBaseConstructorCreation1.js
+++ b/tests/baselines/reference/recursiveBaseConstructorCreation1.js
@@ -8,7 +8,11 @@ var x = new C2(); // Valid
 
 //// [recursiveBaseConstructorCreation1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveClassInstantiationsWithDefaultConstructors.js b/tests/baselines/reference/recursiveClassInstantiationsWithDefaultConstructors.js
index eeda7ef86f4..bfd014a3fe1 100644
--- a/tests/baselines/reference/recursiveClassInstantiationsWithDefaultConstructors.js
+++ b/tests/baselines/reference/recursiveClassInstantiationsWithDefaultConstructors.js
@@ -11,7 +11,11 @@ export class MemberNameArray extends MemberName {
 
 //// [recursiveClassInstantiationsWithDefaultConstructors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveClassReferenceTest.js b/tests/baselines/reference/recursiveClassReferenceTest.js
index e59f3ad4c36..11eb4f8ba8f 100644
--- a/tests/baselines/reference/recursiveClassReferenceTest.js
+++ b/tests/baselines/reference/recursiveClassReferenceTest.js
@@ -106,7 +106,11 @@ module Sample.Thing.Languages.PlainText {
 // Scenario 1: Test reqursive function call with "this" parameter
 // Scenario 2: Test recursive function call with cast and "this" parameter
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursiveClassReferenceTest.js.map b/tests/baselines/reference/recursiveClassReferenceTest.js.map
index 0b9bb8281bc..f322d6f0510 100644
--- a/tests/baselines/reference/recursiveClassReferenceTest.js.map
+++ b/tests/baselines/reference/recursiveClassReferenceTest.js.map
@@ -1,2 +1,2 @@
 //// [recursiveClassReferenceTest.js.map]
-{"version":3,"file":"recursiveClassReferenceTest.js","sourceRoot":"","sources":["recursiveClassReferenceTest.ts"],"names":[],"mappings":"AAAA,iEAAiE;AACjE,0EAA0E;;;;;;AA8B1E,IAAO,MAAM,CAUZ;AAVD,WAAO,MAAM;IAAC,IAAA,OAAO,CAUpB;IAVa,WAAA,OAAO;QAAC,IAAA,KAAK,CAU1B;QAVqB,WAAA,OAAK;YAAC,IAAA,IAAI,CAU/B;YAV2B,WAAA,IAAI;gBAC/B;oBAAA;oBAQA,CAAC;oBANO,+BAAK,GAAZ,cAAiB,MAAM,CAAC,IAAI,CAAC,CAAC,CAAC;oBAExB,6BAAG,GAAV,UAAW,KAA6B;wBAEvC,MAAM,CAAC,IAAI,CAAC;oBACb,CAAC;oBACF,sBAAC;gBAAD,CAAC,AARD,IAQC;gBARY,oBAAe,kBAQ3B,CAAA;YACF,CAAC,EAV2B,IAAI,GAAJ,YAAI,KAAJ,YAAI,QAU/B;QAAD,CAAC,EAVqB,KAAK,GAAL,aAAK,KAAL,aAAK,QAU1B;IAAD,CAAC,EAVa,OAAO,GAAP,cAAO,KAAP,cAAO,QAUpB;AAAD,CAAC,EAVM,MAAM,KAAN,MAAM,QAUZ;AAED,WAAO,MAAM;IAAC,IAAA,KAAK,CAoBlB;IApBa,WAAA,KAAK;QAAC,IAAA,OAAO,CAoB1B;QApBmB,WAAA,OAAO;YAC1B;gBAKC,oBAAoB,SAAkC;oBAAlC,cAAS,GAAT,SAAS,CAAyB;oBAD9C,YAAO,GAAO,IAAI,CAAC;oBAEvB,aAAa;oBACb,SAAS,CAAC,SAAS,CAAC,WAAW,EAAE,IAAI,CAAC,CAAC;gBAC3C,CAAC;gBANM,wBAAG,GAAV,UAAW,MAAyC,IAAI,EAAE,CAAC,CAAC,IAAI,CAAC,CAAC,CAAC;oBAAA,MAAM,CAAC,MAAM,CAAC,IAAI,CAAC,CAAC;gBAAA,CAAC,CAAA,CAAC;gBAQlF,+BAAU,GAAjB;oBACC,MAAM,CAAC,OAAO,CAAC;gBAChB,CAAC;gBAEM,4BAAO,GAAd;gBAEA,CAAC;gBAEF,iBAAC;YAAD,CAAC,AAlBD,IAkBC;YAlBY,kBAAU,aAkBtB,CAAA;QACF,CAAC,EApBmB,OAAO,GAAP,aAAO,KAAP,aAAO,QAoB1B;IAAD,CAAC,EApBa,KAAK,GAAL,YAAK,KAAL,YAAK,QAoBlB;AAAD,CAAC,EApBM,MAAM,KAAN,MAAM,QAoBZ;AAGD;IAAA;IAAuF,CAAC;IAA3C,sCAAe,GAAtB,cAAmC,MAAM,CAAC,IAAI,CAAC,CAAA,CAAC;IAAC,mBAAC;AAAD,CAAC,AAAxF,IAAwF;AASxF,WAAO,MAAM;IAAC,IAAA,KAAK,CAwBlB;IAxBa,WAAA,KAAK;QAAC,IAAA,SAAS,CAwB5B;QAxBmB,WAAA,SAAS;YAAC,IAAA,SAAS,CAwBtC;YAxB6B,WAAA,SAAS;gBAEtC;oBACO,eAAoB,IAAW;wBAAX,SAAI,GAAJ,IAAI,CAAO;oBAAI,CAAC;oBACnC,qBAAK,GAAZ;wBACC,MAAM,CAAC,IAAI,CAAC;oBACb,CAAC;oBAEM,sBAAM,GAAb,UAAc,KAAY;wBACzB,MAAM,CAAC,IAAI,KAAK,KAAK,CAAC;oBACvB,CAAC;oBAEM,uBAAO,GAAd,cAA0B,MAAM,CAAC,IAAI,CAAC,CAAC,CAAC;oBACzC,YAAC;gBAAD,CAAC,AAXD,IAWC;gBAXY,eAAK,QAWjB,CAAA;gBAED;oBAA0B,wBAAY;oBAAtC;;oBAQA,CAAC;oBANA,aAAa;oBACN,8BAAe,GAAtB;wBACC,MAAM,CAAC,IAAI,KAAK,CAAC,IAAI,CAAC,CAAC;oBACxB,CAAC;oBAGF,WAAC;gBAAD,CAAC,AARD,CAA0B,YAAY,GAQrC;gBARY,cAAI,OAQhB,CAAA;YACF,CAAC,EAxB6B,SAAS,GAAT,mBAAS,KAAT,mBAAS,QAwBtC;QAAD,CAAC,EAxBmB,SAAS,GAAT,eAAS,KAAT,eAAS,QAwB5B;IAAD,CAAC,EAxBa,KAAK,GAAL,YAAK,KAAL,YAAK,QAwBlB;AAAD,CAAC,EAxBM,MAAM,KAAN,MAAM,QAwBZ"}
\ No newline at end of file
+{"version":3,"file":"recursiveClassReferenceTest.js","sourceRoot":"","sources":["recursiveClassReferenceTest.ts"],"names":[],"mappings":"AAAA,iEAAiE;AACjE,0EAA0E;;;;;;;;;;AA8B1E,IAAO,MAAM,CAUZ;AAVD,WAAO,MAAM;IAAC,IAAA,OAAO,CAUpB;IAVa,WAAA,OAAO;QAAC,IAAA,KAAK,CAU1B;QAVqB,WAAA,OAAK;YAAC,IAAA,IAAI,CAU/B;YAV2B,WAAA,IAAI;gBAC/B;oBAAA;oBAQA,CAAC;oBANO,+BAAK,GAAZ,cAAiB,MAAM,CAAC,IAAI,CAAC,CAAC,CAAC;oBAExB,6BAAG,GAAV,UAAW,KAA6B;wBAEvC,MAAM,CAAC,IAAI,CAAC;oBACb,CAAC;oBACF,sBAAC;gBAAD,CAAC,AARD,IAQC;gBARY,oBAAe,kBAQ3B,CAAA;YACF,CAAC,EAV2B,IAAI,GAAJ,YAAI,KAAJ,YAAI,QAU/B;QAAD,CAAC,EAVqB,KAAK,GAAL,aAAK,KAAL,aAAK,QAU1B;IAAD,CAAC,EAVa,OAAO,GAAP,cAAO,KAAP,cAAO,QAUpB;AAAD,CAAC,EAVM,MAAM,KAAN,MAAM,QAUZ;AAED,WAAO,MAAM;IAAC,IAAA,KAAK,CAoBlB;IApBa,WAAA,KAAK;QAAC,IAAA,OAAO,CAoB1B;QApBmB,WAAA,OAAO;YAC1B;gBAKC,oBAAoB,SAAkC;oBAAlC,cAAS,GAAT,SAAS,CAAyB;oBAD9C,YAAO,GAAO,IAAI,CAAC;oBAEvB,aAAa;oBACb,SAAS,CAAC,SAAS,CAAC,WAAW,EAAE,IAAI,CAAC,CAAC;gBAC3C,CAAC;gBANM,wBAAG,GAAV,UAAW,MAAyC,IAAI,EAAE,CAAC,CAAC,IAAI,CAAC,CAAC,CAAC;oBAAA,MAAM,CAAC,MAAM,CAAC,IAAI,CAAC,CAAC;gBAAA,CAAC,CAAA,CAAC;gBAQlF,+BAAU,GAAjB;oBACC,MAAM,CAAC,OAAO,CAAC;gBAChB,CAAC;gBAEM,4BAAO,GAAd;gBAEA,CAAC;gBAEF,iBAAC;YAAD,CAAC,AAlBD,IAkBC;YAlBY,kBAAU,aAkBtB,CAAA;QACF,CAAC,EApBmB,OAAO,GAAP,aAAO,KAAP,aAAO,QAoB1B;IAAD,CAAC,EApBa,KAAK,GAAL,YAAK,KAAL,YAAK,QAoBlB;AAAD,CAAC,EApBM,MAAM,KAAN,MAAM,QAoBZ;AAGD;IAAA;IAAuF,CAAC;IAA3C,sCAAe,GAAtB,cAAmC,MAAM,CAAC,IAAI,CAAC,CAAA,CAAC;IAAC,mBAAC;AAAD,CAAC,AAAxF,IAAwF;AASxF,WAAO,MAAM;IAAC,IAAA,KAAK,CAwBlB;IAxBa,WAAA,KAAK;QAAC,IAAA,SAAS,CAwB5B;QAxBmB,WAAA,SAAS;YAAC,IAAA,SAAS,CAwBtC;YAxB6B,WAAA,SAAS;gBAEtC;oBACO,eAAoB,IAAW;wBAAX,SAAI,GAAJ,IAAI,CAAO;oBAAI,CAAC;oBACnC,qBAAK,GAAZ;wBACC,MAAM,CAAC,IAAI,CAAC;oBACb,CAAC;oBAEM,sBAAM,GAAb,UAAc,KAAY;wBACzB,MAAM,CAAC,IAAI,KAAK,KAAK,CAAC;oBACvB,CAAC;oBAEM,uBAAO,GAAd,cAA0B,MAAM,CAAC,IAAI,CAAC,CAAC,CAAC;oBACzC,YAAC;gBAAD,CAAC,AAXD,IAWC;gBAXY,eAAK,QAWjB,CAAA;gBAED;oBAA0B,wBAAY;oBAAtC;;oBAQA,CAAC;oBANA,aAAa;oBACN,8BAAe,GAAtB;wBACC,MAAM,CAAC,IAAI,KAAK,CAAC,IAAI,CAAC,CAAC;oBACxB,CAAC;oBAGF,WAAC;gBAAD,CAAC,AARD,CAA0B,YAAY,GAQrC;gBARY,cAAI,OAQhB,CAAA;YACF,CAAC,EAxB6B,SAAS,GAAT,mBAAS,KAAT,mBAAS,QAwBtC;QAAD,CAAC,EAxBmB,SAAS,GAAT,eAAS,KAAT,eAAS,QAwB5B;IAAD,CAAC,EAxBa,KAAK,GAAL,YAAK,KAAL,YAAK,QAwBlB;AAAD,CAAC,EAxBM,MAAM,KAAN,MAAM,QAwBZ"}
\ No newline at end of file
diff --git a/tests/baselines/reference/recursiveClassReferenceTest.sourcemap.txt b/tests/baselines/reference/recursiveClassReferenceTest.sourcemap.txt
index 8bfac267dbf..5bb43de1b9f 100644
--- a/tests/baselines/reference/recursiveClassReferenceTest.sourcemap.txt
+++ b/tests/baselines/reference/recursiveClassReferenceTest.sourcemap.txt
@@ -27,7 +27,11 @@ sourceFile:recursiveClassReferenceTest.ts
 2 >Emitted(2, 75) Source(2, 75) + SourceIndex(0)
 ---
 >>>var __extends = (this && this.__extends) || function (d, b) {
->>>    Object.setPrototypeOf(d, b);
+>>>    if (typeof Object.setPrototypeOf === "function") {
+>>>        Object.setPrototypeOf(d, b);
+>>>    } else {
+>>>        d.__proto__ = b;
+>>>    }
 >>>    function __() { this.constructor = d; }
 >>>    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 >>>};
@@ -81,10 +85,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >          		}
   >          	}
   >          }
-1 >Emitted(8, 1) Source(32, 1) + SourceIndex(0)
-2 >Emitted(8, 5) Source(32, 8) + SourceIndex(0)
-3 >Emitted(8, 11) Source(32, 14) + SourceIndex(0)
-4 >Emitted(8, 12) Source(42, 2) + SourceIndex(0)
+1 >Emitted(12, 1) Source(32, 1) + SourceIndex(0)
+2 >Emitted(12, 5) Source(32, 8) + SourceIndex(0)
+3 >Emitted(12, 11) Source(32, 14) + SourceIndex(0)
+4 >Emitted(12, 12) Source(42, 2) + SourceIndex(0)
 ---
 >>>(function (Sample) {
 1->
@@ -93,9 +97,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >module 
 3 >           Sample
-1->Emitted(9, 1) Source(32, 1) + SourceIndex(0)
-2 >Emitted(9, 12) Source(32, 8) + SourceIndex(0)
-3 >Emitted(9, 18) Source(32, 14) + SourceIndex(0)
+1->Emitted(13, 1) Source(32, 1) + SourceIndex(0)
+2 >Emitted(13, 12) Source(32, 8) + SourceIndex(0)
+3 >Emitted(13, 18) Source(32, 14) + SourceIndex(0)
 ---
 >>>    var Actions;
 1 >^^^^
@@ -117,10 +121,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >               		}
   >               	}
   >               }
-1 >Emitted(10, 5) Source(32, 15) + SourceIndex(0)
-2 >Emitted(10, 9) Source(32, 15) + SourceIndex(0)
-3 >Emitted(10, 16) Source(32, 22) + SourceIndex(0)
-4 >Emitted(10, 17) Source(42, 2) + SourceIndex(0)
+1 >Emitted(14, 5) Source(32, 15) + SourceIndex(0)
+2 >Emitted(14, 9) Source(32, 15) + SourceIndex(0)
+3 >Emitted(14, 16) Source(32, 22) + SourceIndex(0)
+4 >Emitted(14, 17) Source(42, 2) + SourceIndex(0)
 ---
 >>>    (function (Actions) {
 1->^^^^
@@ -129,9 +133,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >    
 3 >               Actions
-1->Emitted(11, 5) Source(32, 15) + SourceIndex(0)
-2 >Emitted(11, 16) Source(32, 15) + SourceIndex(0)
-3 >Emitted(11, 23) Source(32, 22) + SourceIndex(0)
+1->Emitted(15, 5) Source(32, 15) + SourceIndex(0)
+2 >Emitted(15, 16) Source(32, 15) + SourceIndex(0)
+3 >Emitted(15, 23) Source(32, 22) + SourceIndex(0)
 ---
 >>>        var Thing;
 1 >^^^^^^^^
@@ -153,10 +157,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                 		}
   >                 	}
   >                 }
-1 >Emitted(12, 9) Source(32, 23) + SourceIndex(0)
-2 >Emitted(12, 13) Source(32, 23) + SourceIndex(0)
-3 >Emitted(12, 18) Source(32, 28) + SourceIndex(0)
-4 >Emitted(12, 19) Source(42, 2) + SourceIndex(0)
+1 >Emitted(16, 9) Source(32, 23) + SourceIndex(0)
+2 >Emitted(16, 13) Source(32, 23) + SourceIndex(0)
+3 >Emitted(16, 18) Source(32, 28) + SourceIndex(0)
+4 >Emitted(16, 19) Source(42, 2) + SourceIndex(0)
 ---
 >>>        (function (Thing_1) {
 1->^^^^^^^^
@@ -165,9 +169,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >        
 3 >                   Thing
-1->Emitted(13, 9) Source(32, 23) + SourceIndex(0)
-2 >Emitted(13, 20) Source(32, 23) + SourceIndex(0)
-3 >Emitted(13, 27) Source(32, 28) + SourceIndex(0)
+1->Emitted(17, 9) Source(32, 23) + SourceIndex(0)
+2 >Emitted(17, 20) Source(32, 23) + SourceIndex(0)
+3 >Emitted(17, 27) Source(32, 28) + SourceIndex(0)
 ---
 >>>            var Find;
 1 >^^^^^^^^^^^^
@@ -189,10 +193,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                    		}
   >                    	}
   >                    }
-1 >Emitted(14, 13) Source(32, 29) + SourceIndex(0)
-2 >Emitted(14, 17) Source(32, 29) + SourceIndex(0)
-3 >Emitted(14, 21) Source(32, 33) + SourceIndex(0)
-4 >Emitted(14, 22) Source(42, 2) + SourceIndex(0)
+1 >Emitted(18, 13) Source(32, 29) + SourceIndex(0)
+2 >Emitted(18, 17) Source(32, 29) + SourceIndex(0)
+3 >Emitted(18, 21) Source(32, 33) + SourceIndex(0)
+4 >Emitted(18, 22) Source(42, 2) + SourceIndex(0)
 ---
 >>>            (function (Find) {
 1->^^^^^^^^^^^^
@@ -202,22 +206,22 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >            
 3 >                       Find
-1->Emitted(15, 13) Source(32, 29) + SourceIndex(0)
-2 >Emitted(15, 24) Source(32, 29) + SourceIndex(0)
-3 >Emitted(15, 28) Source(32, 33) + SourceIndex(0)
+1->Emitted(19, 13) Source(32, 29) + SourceIndex(0)
+2 >Emitted(19, 24) Source(32, 29) + SourceIndex(0)
+3 >Emitted(19, 28) Source(32, 33) + SourceIndex(0)
 ---
 >>>                var StartFindAction = (function () {
 1->^^^^^^^^^^^^^^^^
 2 >                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1-> {
   >	
-1->Emitted(16, 17) Source(33, 2) + SourceIndex(0)
+1->Emitted(20, 17) Source(33, 2) + SourceIndex(0)
 ---
 >>>                    function StartFindAction() {
 1->^^^^^^^^^^^^^^^^^^^^
 2 >                    ^^->
 1->
-1->Emitted(17, 21) Source(33, 2) + SourceIndex(0)
+1->Emitted(21, 21) Source(33, 2) + SourceIndex(0)
 ---
 >>>                    }
 1->^^^^^^^^^^^^^^^^^^^^
@@ -233,8 +237,8 @@ sourceFile:recursiveClassReferenceTest.ts
   >		}
   >	
 2 >                    }
-1->Emitted(18, 21) Source(41, 2) + SourceIndex(0)
-2 >Emitted(18, 22) Source(41, 3) + SourceIndex(0)
+1->Emitted(22, 21) Source(41, 2) + SourceIndex(0)
+2 >Emitted(22, 22) Source(41, 3) + SourceIndex(0)
 ---
 >>>                    StartFindAction.prototype.getId = function () { return "yo"; };
 1->^^^^^^^^^^^^^^^^^^^^
@@ -257,16 +261,16 @@ sourceFile:recursiveClassReferenceTest.ts
 8 >                                                                               ;
 9 >                                                                                 
 10>                                                                                 }
-1->Emitted(19, 21) Source(35, 10) + SourceIndex(0)
-2 >Emitted(19, 52) Source(35, 15) + SourceIndex(0)
-3 >Emitted(19, 55) Source(35, 3) + SourceIndex(0)
-4 >Emitted(19, 69) Source(35, 20) + SourceIndex(0)
-5 >Emitted(19, 75) Source(35, 26) + SourceIndex(0)
-6 >Emitted(19, 76) Source(35, 27) + SourceIndex(0)
-7 >Emitted(19, 80) Source(35, 31) + SourceIndex(0)
-8 >Emitted(19, 81) Source(35, 32) + SourceIndex(0)
-9 >Emitted(19, 82) Source(35, 33) + SourceIndex(0)
-10>Emitted(19, 83) Source(35, 34) + SourceIndex(0)
+1->Emitted(23, 21) Source(35, 10) + SourceIndex(0)
+2 >Emitted(23, 52) Source(35, 15) + SourceIndex(0)
+3 >Emitted(23, 55) Source(35, 3) + SourceIndex(0)
+4 >Emitted(23, 69) Source(35, 20) + SourceIndex(0)
+5 >Emitted(23, 75) Source(35, 26) + SourceIndex(0)
+6 >Emitted(23, 76) Source(35, 27) + SourceIndex(0)
+7 >Emitted(23, 80) Source(35, 31) + SourceIndex(0)
+8 >Emitted(23, 81) Source(35, 32) + SourceIndex(0)
+9 >Emitted(23, 82) Source(35, 33) + SourceIndex(0)
+10>Emitted(23, 83) Source(35, 34) + SourceIndex(0)
 ---
 >>>                    StartFindAction.prototype.run = function (Thing) {
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -281,11 +285,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                                                 
 4 >                                                    public run(
 5 >                                                              Thing:Sample.Thing.ICodeThing
-1 >Emitted(20, 21) Source(37, 10) + SourceIndex(0)
-2 >Emitted(20, 50) Source(37, 13) + SourceIndex(0)
-3 >Emitted(20, 53) Source(37, 3) + SourceIndex(0)
-4 >Emitted(20, 63) Source(37, 14) + SourceIndex(0)
-5 >Emitted(20, 68) Source(37, 43) + SourceIndex(0)
+1 >Emitted(24, 21) Source(37, 10) + SourceIndex(0)
+2 >Emitted(24, 50) Source(37, 13) + SourceIndex(0)
+3 >Emitted(24, 53) Source(37, 3) + SourceIndex(0)
+4 >Emitted(24, 63) Source(37, 14) + SourceIndex(0)
+5 >Emitted(24, 68) Source(37, 43) + SourceIndex(0)
 ---
 >>>                        return true;
 1 >^^^^^^^^^^^^^^^^^^^^^^^^
@@ -300,11 +304,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                               
 4 >                               true
 5 >                                   ;
-1 >Emitted(21, 25) Source(39, 4) + SourceIndex(0)
-2 >Emitted(21, 31) Source(39, 10) + SourceIndex(0)
-3 >Emitted(21, 32) Source(39, 11) + SourceIndex(0)
-4 >Emitted(21, 36) Source(39, 15) + SourceIndex(0)
-5 >Emitted(21, 37) Source(39, 16) + SourceIndex(0)
+1 >Emitted(25, 25) Source(39, 4) + SourceIndex(0)
+2 >Emitted(25, 31) Source(39, 10) + SourceIndex(0)
+3 >Emitted(25, 32) Source(39, 11) + SourceIndex(0)
+4 >Emitted(25, 36) Source(39, 15) + SourceIndex(0)
+5 >Emitted(25, 37) Source(39, 16) + SourceIndex(0)
 ---
 >>>                    };
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -313,8 +317,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >		
 2 >                    }
-1 >Emitted(22, 21) Source(40, 3) + SourceIndex(0)
-2 >Emitted(22, 22) Source(40, 4) + SourceIndex(0)
+1 >Emitted(26, 21) Source(40, 3) + SourceIndex(0)
+2 >Emitted(26, 22) Source(40, 4) + SourceIndex(0)
 ---
 >>>                    return StartFindAction;
 1->^^^^^^^^^^^^^^^^^^^^
@@ -322,8 +326,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
   >	
 2 >                    }
-1->Emitted(23, 21) Source(41, 2) + SourceIndex(0)
-2 >Emitted(23, 43) Source(41, 3) + SourceIndex(0)
+1->Emitted(27, 21) Source(41, 2) + SourceIndex(0)
+2 >Emitted(27, 43) Source(41, 3) + SourceIndex(0)
 ---
 >>>                }());
 1 >^^^^^^^^^^^^^^^^
@@ -343,10 +347,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                 			return true;
   >                 		}
   >                 	}
-1 >Emitted(24, 17) Source(41, 2) + SourceIndex(0)
-2 >Emitted(24, 18) Source(41, 3) + SourceIndex(0)
-3 >Emitted(24, 18) Source(33, 2) + SourceIndex(0)
-4 >Emitted(24, 22) Source(41, 3) + SourceIndex(0)
+1 >Emitted(28, 17) Source(41, 2) + SourceIndex(0)
+2 >Emitted(28, 18) Source(41, 3) + SourceIndex(0)
+3 >Emitted(28, 18) Source(33, 2) + SourceIndex(0)
+4 >Emitted(28, 22) Source(41, 3) + SourceIndex(0)
 ---
 >>>                Find.StartFindAction = StartFindAction;
 1->^^^^^^^^^^^^^^^^
@@ -366,10 +370,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                    		}
   >                                    	}
 4 >                                                      
-1->Emitted(25, 17) Source(33, 15) + SourceIndex(0)
-2 >Emitted(25, 37) Source(33, 30) + SourceIndex(0)
-3 >Emitted(25, 55) Source(41, 3) + SourceIndex(0)
-4 >Emitted(25, 56) Source(41, 3) + SourceIndex(0)
+1->Emitted(29, 17) Source(33, 15) + SourceIndex(0)
+2 >Emitted(29, 37) Source(33, 30) + SourceIndex(0)
+3 >Emitted(29, 55) Source(41, 3) + SourceIndex(0)
+4 >Emitted(29, 56) Source(41, 3) + SourceIndex(0)
 ---
 >>>            })(Find = Thing_1.Find || (Thing_1.Find = {}));
 1->^^^^^^^^^^^^
@@ -401,15 +405,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                                   		}
   >                                                   	}
   >                                                   }
-1->Emitted(26, 13) Source(42, 1) + SourceIndex(0)
-2 >Emitted(26, 14) Source(42, 2) + SourceIndex(0)
-3 >Emitted(26, 16) Source(32, 29) + SourceIndex(0)
-4 >Emitted(26, 20) Source(32, 33) + SourceIndex(0)
-5 >Emitted(26, 23) Source(32, 29) + SourceIndex(0)
-6 >Emitted(26, 35) Source(32, 33) + SourceIndex(0)
-7 >Emitted(26, 40) Source(32, 29) + SourceIndex(0)
-8 >Emitted(26, 52) Source(32, 33) + SourceIndex(0)
-9 >Emitted(26, 60) Source(42, 2) + SourceIndex(0)
+1->Emitted(30, 13) Source(42, 1) + SourceIndex(0)
+2 >Emitted(30, 14) Source(42, 2) + SourceIndex(0)
+3 >Emitted(30, 16) Source(32, 29) + SourceIndex(0)
+4 >Emitted(30, 20) Source(32, 33) + SourceIndex(0)
+5 >Emitted(30, 23) Source(32, 29) + SourceIndex(0)
+6 >Emitted(30, 35) Source(32, 33) + SourceIndex(0)
+7 >Emitted(30, 40) Source(32, 29) + SourceIndex(0)
+8 >Emitted(30, 52) Source(32, 33) + SourceIndex(0)
+9 >Emitted(30, 60) Source(42, 2) + SourceIndex(0)
 ---
 >>>        })(Thing = Actions.Thing || (Actions.Thing = {}));
 1 >^^^^^^^^
@@ -441,15 +445,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                                  		}
   >                                                  	}
   >                                                  }
-1 >Emitted(27, 9) Source(42, 1) + SourceIndex(0)
-2 >Emitted(27, 10) Source(42, 2) + SourceIndex(0)
-3 >Emitted(27, 12) Source(32, 23) + SourceIndex(0)
-4 >Emitted(27, 17) Source(32, 28) + SourceIndex(0)
-5 >Emitted(27, 20) Source(32, 23) + SourceIndex(0)
-6 >Emitted(27, 33) Source(32, 28) + SourceIndex(0)
-7 >Emitted(27, 38) Source(32, 23) + SourceIndex(0)
-8 >Emitted(27, 51) Source(32, 28) + SourceIndex(0)
-9 >Emitted(27, 59) Source(42, 2) + SourceIndex(0)
+1 >Emitted(31, 9) Source(42, 1) + SourceIndex(0)
+2 >Emitted(31, 10) Source(42, 2) + SourceIndex(0)
+3 >Emitted(31, 12) Source(32, 23) + SourceIndex(0)
+4 >Emitted(31, 17) Source(32, 28) + SourceIndex(0)
+5 >Emitted(31, 20) Source(32, 23) + SourceIndex(0)
+6 >Emitted(31, 33) Source(32, 28) + SourceIndex(0)
+7 >Emitted(31, 38) Source(32, 23) + SourceIndex(0)
+8 >Emitted(31, 51) Source(32, 28) + SourceIndex(0)
+9 >Emitted(31, 59) Source(42, 2) + SourceIndex(0)
 ---
 >>>    })(Actions = Sample.Actions || (Sample.Actions = {}));
 1->^^^^
@@ -480,15 +484,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                                  		}
   >                                                  	}
   >                                                  }
-1->Emitted(28, 5) Source(42, 1) + SourceIndex(0)
-2 >Emitted(28, 6) Source(42, 2) + SourceIndex(0)
-3 >Emitted(28, 8) Source(32, 15) + SourceIndex(0)
-4 >Emitted(28, 15) Source(32, 22) + SourceIndex(0)
-5 >Emitted(28, 18) Source(32, 15) + SourceIndex(0)
-6 >Emitted(28, 32) Source(32, 22) + SourceIndex(0)
-7 >Emitted(28, 37) Source(32, 15) + SourceIndex(0)
-8 >Emitted(28, 51) Source(32, 22) + SourceIndex(0)
-9 >Emitted(28, 59) Source(42, 2) + SourceIndex(0)
+1->Emitted(32, 5) Source(42, 1) + SourceIndex(0)
+2 >Emitted(32, 6) Source(42, 2) + SourceIndex(0)
+3 >Emitted(32, 8) Source(32, 15) + SourceIndex(0)
+4 >Emitted(32, 15) Source(32, 22) + SourceIndex(0)
+5 >Emitted(32, 18) Source(32, 15) + SourceIndex(0)
+6 >Emitted(32, 32) Source(32, 22) + SourceIndex(0)
+7 >Emitted(32, 37) Source(32, 15) + SourceIndex(0)
+8 >Emitted(32, 51) Source(32, 22) + SourceIndex(0)
+9 >Emitted(32, 59) Source(42, 2) + SourceIndex(0)
 ---
 >>>})(Sample || (Sample = {}));
 1 >
@@ -515,13 +519,13 @@ sourceFile:recursiveClassReferenceTest.ts
   >                    		}
   >                    	}
   >                    }
-1 >Emitted(29, 1) Source(42, 1) + SourceIndex(0)
-2 >Emitted(29, 2) Source(42, 2) + SourceIndex(0)
-3 >Emitted(29, 4) Source(32, 8) + SourceIndex(0)
-4 >Emitted(29, 10) Source(32, 14) + SourceIndex(0)
-5 >Emitted(29, 15) Source(32, 8) + SourceIndex(0)
-6 >Emitted(29, 21) Source(32, 14) + SourceIndex(0)
-7 >Emitted(29, 29) Source(42, 2) + SourceIndex(0)
+1 >Emitted(33, 1) Source(42, 1) + SourceIndex(0)
+2 >Emitted(33, 2) Source(42, 2) + SourceIndex(0)
+3 >Emitted(33, 4) Source(32, 8) + SourceIndex(0)
+4 >Emitted(33, 10) Source(32, 14) + SourceIndex(0)
+5 >Emitted(33, 15) Source(32, 8) + SourceIndex(0)
+6 >Emitted(33, 21) Source(32, 14) + SourceIndex(0)
+7 >Emitted(33, 29) Source(42, 2) + SourceIndex(0)
 ---
 >>>(function (Sample) {
 1 >
@@ -532,9 +536,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >
 2 >module 
 3 >           Sample
-1 >Emitted(30, 1) Source(44, 1) + SourceIndex(0)
-2 >Emitted(30, 12) Source(44, 8) + SourceIndex(0)
-3 >Emitted(30, 18) Source(44, 14) + SourceIndex(0)
+1 >Emitted(34, 1) Source(44, 1) + SourceIndex(0)
+2 >Emitted(34, 12) Source(44, 8) + SourceIndex(0)
+3 >Emitted(34, 18) Source(44, 14) + SourceIndex(0)
 ---
 >>>    var Thing;
 1 >^^^^
@@ -566,10 +570,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >             
   >             	}
   >             }
-1 >Emitted(31, 5) Source(44, 15) + SourceIndex(0)
-2 >Emitted(31, 9) Source(44, 15) + SourceIndex(0)
-3 >Emitted(31, 14) Source(44, 20) + SourceIndex(0)
-4 >Emitted(31, 15) Source(64, 2) + SourceIndex(0)
+1 >Emitted(35, 5) Source(44, 15) + SourceIndex(0)
+2 >Emitted(35, 9) Source(44, 15) + SourceIndex(0)
+3 >Emitted(35, 14) Source(44, 20) + SourceIndex(0)
+4 >Emitted(35, 15) Source(64, 2) + SourceIndex(0)
 ---
 >>>    (function (Thing) {
 1->^^^^
@@ -579,9 +583,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >    
 3 >               Thing
-1->Emitted(32, 5) Source(44, 15) + SourceIndex(0)
-2 >Emitted(32, 16) Source(44, 15) + SourceIndex(0)
-3 >Emitted(32, 21) Source(44, 20) + SourceIndex(0)
+1->Emitted(36, 5) Source(44, 15) + SourceIndex(0)
+2 >Emitted(36, 16) Source(44, 15) + SourceIndex(0)
+3 >Emitted(36, 21) Source(44, 20) + SourceIndex(0)
 ---
 >>>        var Widgets;
 1->^^^^^^^^
@@ -613,10 +617,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                   
   >                   	}
   >                   }
-1->Emitted(33, 9) Source(44, 21) + SourceIndex(0)
-2 >Emitted(33, 13) Source(44, 21) + SourceIndex(0)
-3 >Emitted(33, 20) Source(44, 28) + SourceIndex(0)
-4 >Emitted(33, 21) Source(64, 2) + SourceIndex(0)
+1->Emitted(37, 9) Source(44, 21) + SourceIndex(0)
+2 >Emitted(37, 13) Source(44, 21) + SourceIndex(0)
+3 >Emitted(37, 20) Source(44, 28) + SourceIndex(0)
+4 >Emitted(37, 21) Source(64, 2) + SourceIndex(0)
 ---
 >>>        (function (Widgets) {
 1->^^^^^^^^
@@ -626,16 +630,16 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >        
 3 >                   Widgets
-1->Emitted(34, 9) Source(44, 21) + SourceIndex(0)
-2 >Emitted(34, 20) Source(44, 21) + SourceIndex(0)
-3 >Emitted(34, 27) Source(44, 28) + SourceIndex(0)
+1->Emitted(38, 9) Source(44, 21) + SourceIndex(0)
+2 >Emitted(38, 20) Source(44, 21) + SourceIndex(0)
+3 >Emitted(38, 27) Source(44, 28) + SourceIndex(0)
 ---
 >>>            var FindWidget = (function () {
 1->^^^^^^^^^^^^
 2 >            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1-> {
   >	
-1->Emitted(35, 13) Source(45, 2) + SourceIndex(0)
+1->Emitted(39, 13) Source(45, 2) + SourceIndex(0)
 ---
 >>>                function FindWidget(codeThing) {
 1->^^^^^^^^^^^^^^^^
@@ -650,9 +654,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >		
 2 >                constructor(private 
 3 >                                    codeThing: Sample.Thing.ICodeThing
-1->Emitted(36, 17) Source(50, 3) + SourceIndex(0)
-2 >Emitted(36, 37) Source(50, 23) + SourceIndex(0)
-3 >Emitted(36, 46) Source(50, 57) + SourceIndex(0)
+1->Emitted(40, 17) Source(50, 3) + SourceIndex(0)
+2 >Emitted(40, 37) Source(50, 23) + SourceIndex(0)
+3 >Emitted(40, 46) Source(50, 57) + SourceIndex(0)
 ---
 >>>                    this.codeThing = codeThing;
 1->^^^^^^^^^^^^^^^^^^^^
@@ -665,11 +669,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                                  
 4 >                                     codeThing
 5 >                                              : Sample.Thing.ICodeThing
-1->Emitted(37, 21) Source(50, 23) + SourceIndex(0)
-2 >Emitted(37, 35) Source(50, 32) + SourceIndex(0)
-3 >Emitted(37, 38) Source(50, 23) + SourceIndex(0)
-4 >Emitted(37, 47) Source(50, 32) + SourceIndex(0)
-5 >Emitted(37, 48) Source(50, 57) + SourceIndex(0)
+1->Emitted(41, 21) Source(50, 23) + SourceIndex(0)
+2 >Emitted(41, 35) Source(50, 32) + SourceIndex(0)
+3 >Emitted(41, 38) Source(50, 23) + SourceIndex(0)
+4 >Emitted(41, 47) Source(50, 32) + SourceIndex(0)
+5 >Emitted(41, 48) Source(50, 57) + SourceIndex(0)
 ---
 >>>                    this.domNode = null;
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -682,11 +686,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                                :any = 
 4 >                                   null
 5 >                                       ;
-1 >Emitted(38, 21) Source(49, 11) + SourceIndex(0)
-2 >Emitted(38, 33) Source(49, 18) + SourceIndex(0)
-3 >Emitted(38, 36) Source(49, 25) + SourceIndex(0)
-4 >Emitted(38, 40) Source(49, 29) + SourceIndex(0)
-5 >Emitted(38, 41) Source(49, 30) + SourceIndex(0)
+1 >Emitted(42, 21) Source(49, 11) + SourceIndex(0)
+2 >Emitted(42, 33) Source(49, 18) + SourceIndex(0)
+3 >Emitted(42, 36) Source(49, 25) + SourceIndex(0)
+4 >Emitted(42, 40) Source(49, 29) + SourceIndex(0)
+5 >Emitted(42, 41) Source(49, 30) + SourceIndex(0)
 ---
 >>>                    // scenario 1
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -696,8 +700,8 @@ sourceFile:recursiveClassReferenceTest.ts
   >		constructor(private codeThing: Sample.Thing.ICodeThing) {
   >		    
 2 >                    // scenario 1
-1 >Emitted(39, 21) Source(51, 7) + SourceIndex(0)
-2 >Emitted(39, 34) Source(51, 20) + SourceIndex(0)
+1 >Emitted(43, 21) Source(51, 7) + SourceIndex(0)
+2 >Emitted(43, 34) Source(51, 20) + SourceIndex(0)
 ---
 >>>                    codeThing.addWidget("addWidget", this);
 1->^^^^^^^^^^^^^^^^^^^^
@@ -721,16 +725,16 @@ sourceFile:recursiveClassReferenceTest.ts
 8 >                                                     this
 9 >                                                         )
 10>                                                          ;
-1->Emitted(40, 21) Source(52, 7) + SourceIndex(0)
-2 >Emitted(40, 30) Source(52, 16) + SourceIndex(0)
-3 >Emitted(40, 31) Source(52, 17) + SourceIndex(0)
-4 >Emitted(40, 40) Source(52, 26) + SourceIndex(0)
-5 >Emitted(40, 41) Source(52, 27) + SourceIndex(0)
-6 >Emitted(40, 52) Source(52, 38) + SourceIndex(0)
-7 >Emitted(40, 54) Source(52, 40) + SourceIndex(0)
-8 >Emitted(40, 58) Source(52, 44) + SourceIndex(0)
-9 >Emitted(40, 59) Source(52, 45) + SourceIndex(0)
-10>Emitted(40, 60) Source(52, 46) + SourceIndex(0)
+1->Emitted(44, 21) Source(52, 7) + SourceIndex(0)
+2 >Emitted(44, 30) Source(52, 16) + SourceIndex(0)
+3 >Emitted(44, 31) Source(52, 17) + SourceIndex(0)
+4 >Emitted(44, 40) Source(52, 26) + SourceIndex(0)
+5 >Emitted(44, 41) Source(52, 27) + SourceIndex(0)
+6 >Emitted(44, 52) Source(52, 38) + SourceIndex(0)
+7 >Emitted(44, 54) Source(52, 40) + SourceIndex(0)
+8 >Emitted(44, 58) Source(52, 44) + SourceIndex(0)
+9 >Emitted(44, 59) Source(52, 45) + SourceIndex(0)
+10>Emitted(44, 60) Source(52, 46) + SourceIndex(0)
 ---
 >>>                }
 1 >^^^^^^^^^^^^^^^^
@@ -739,8 +743,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >		
 2 >                }
-1 >Emitted(41, 17) Source(53, 3) + SourceIndex(0)
-2 >Emitted(41, 18) Source(53, 4) + SourceIndex(0)
+1 >Emitted(45, 17) Source(53, 3) + SourceIndex(0)
+2 >Emitted(45, 18) Source(53, 4) + SourceIndex(0)
 ---
 >>>                FindWidget.prototype.gar = function (runner) { if (true) {
 1->^^^^^^^^^^^^^^^^
@@ -769,19 +773,19 @@ sourceFile:recursiveClassReferenceTest.ts
 11>                                                                       )
 12>                                                                         
 13>                                                                         {
-1->Emitted(42, 17) Source(47, 10) + SourceIndex(0)
-2 >Emitted(42, 41) Source(47, 13) + SourceIndex(0)
-3 >Emitted(42, 44) Source(47, 3) + SourceIndex(0)
-4 >Emitted(42, 54) Source(47, 14) + SourceIndex(0)
-5 >Emitted(42, 60) Source(47, 55) + SourceIndex(0)
-6 >Emitted(42, 64) Source(47, 59) + SourceIndex(0)
-7 >Emitted(42, 66) Source(47, 61) + SourceIndex(0)
-8 >Emitted(42, 67) Source(47, 62) + SourceIndex(0)
-9 >Emitted(42, 68) Source(47, 63) + SourceIndex(0)
-10>Emitted(42, 72) Source(47, 67) + SourceIndex(0)
-11>Emitted(42, 73) Source(47, 68) + SourceIndex(0)
-12>Emitted(42, 74) Source(47, 69) + SourceIndex(0)
-13>Emitted(42, 75) Source(47, 70) + SourceIndex(0)
+1->Emitted(46, 17) Source(47, 10) + SourceIndex(0)
+2 >Emitted(46, 41) Source(47, 13) + SourceIndex(0)
+3 >Emitted(46, 44) Source(47, 3) + SourceIndex(0)
+4 >Emitted(46, 54) Source(47, 14) + SourceIndex(0)
+5 >Emitted(46, 60) Source(47, 55) + SourceIndex(0)
+6 >Emitted(46, 64) Source(47, 59) + SourceIndex(0)
+7 >Emitted(46, 66) Source(47, 61) + SourceIndex(0)
+8 >Emitted(46, 67) Source(47, 62) + SourceIndex(0)
+9 >Emitted(46, 68) Source(47, 63) + SourceIndex(0)
+10>Emitted(46, 72) Source(47, 67) + SourceIndex(0)
+11>Emitted(46, 73) Source(47, 68) + SourceIndex(0)
+12>Emitted(46, 74) Source(47, 69) + SourceIndex(0)
+13>Emitted(46, 75) Source(47, 70) + SourceIndex(0)
 ---
 >>>                    return runner(this);
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -800,14 +804,14 @@ sourceFile:recursiveClassReferenceTest.ts
 6 >                                  this
 7 >                                      )
 8 >                                       ;
-1 >Emitted(43, 21) Source(47, 70) + SourceIndex(0)
-2 >Emitted(43, 27) Source(47, 76) + SourceIndex(0)
-3 >Emitted(43, 28) Source(47, 77) + SourceIndex(0)
-4 >Emitted(43, 34) Source(47, 83) + SourceIndex(0)
-5 >Emitted(43, 35) Source(47, 84) + SourceIndex(0)
-6 >Emitted(43, 39) Source(47, 88) + SourceIndex(0)
-7 >Emitted(43, 40) Source(47, 89) + SourceIndex(0)
-8 >Emitted(43, 41) Source(47, 90) + SourceIndex(0)
+1 >Emitted(47, 21) Source(47, 70) + SourceIndex(0)
+2 >Emitted(47, 27) Source(47, 76) + SourceIndex(0)
+3 >Emitted(47, 28) Source(47, 77) + SourceIndex(0)
+4 >Emitted(47, 34) Source(47, 83) + SourceIndex(0)
+5 >Emitted(47, 35) Source(47, 84) + SourceIndex(0)
+6 >Emitted(47, 39) Source(47, 88) + SourceIndex(0)
+7 >Emitted(47, 40) Source(47, 89) + SourceIndex(0)
+8 >Emitted(47, 41) Source(47, 90) + SourceIndex(0)
 ---
 >>>                } };
 1 >^^^^^^^^^^^^^^^^
@@ -819,10 +823,10 @@ sourceFile:recursiveClassReferenceTest.ts
 2 >                }
 3 >                 
 4 >                  }
-1 >Emitted(44, 17) Source(47, 90) + SourceIndex(0)
-2 >Emitted(44, 18) Source(47, 91) + SourceIndex(0)
-3 >Emitted(44, 19) Source(47, 91) + SourceIndex(0)
-4 >Emitted(44, 20) Source(47, 92) + SourceIndex(0)
+1 >Emitted(48, 17) Source(47, 90) + SourceIndex(0)
+2 >Emitted(48, 18) Source(47, 91) + SourceIndex(0)
+3 >Emitted(48, 19) Source(47, 91) + SourceIndex(0)
+4 >Emitted(48, 20) Source(47, 92) + SourceIndex(0)
 ---
 >>>                FindWidget.prototype.getDomNode = function () {
 1->^^^^^^^^^^^^^^^^
@@ -839,9 +843,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >		public 
 2 >                getDomNode
 3 >                                               
-1->Emitted(45, 17) Source(55, 10) + SourceIndex(0)
-2 >Emitted(45, 48) Source(55, 20) + SourceIndex(0)
-3 >Emitted(45, 51) Source(55, 3) + SourceIndex(0)
+1->Emitted(49, 17) Source(55, 10) + SourceIndex(0)
+2 >Emitted(49, 48) Source(55, 20) + SourceIndex(0)
+3 >Emitted(49, 51) Source(55, 3) + SourceIndex(0)
 ---
 >>>                    return domNode;
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -855,11 +859,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                           
 4 >                           domNode
 5 >                                  ;
-1 >Emitted(46, 21) Source(56, 4) + SourceIndex(0)
-2 >Emitted(46, 27) Source(56, 10) + SourceIndex(0)
-3 >Emitted(46, 28) Source(56, 11) + SourceIndex(0)
-4 >Emitted(46, 35) Source(56, 18) + SourceIndex(0)
-5 >Emitted(46, 36) Source(56, 19) + SourceIndex(0)
+1 >Emitted(50, 21) Source(56, 4) + SourceIndex(0)
+2 >Emitted(50, 27) Source(56, 10) + SourceIndex(0)
+3 >Emitted(50, 28) Source(56, 11) + SourceIndex(0)
+4 >Emitted(50, 35) Source(56, 18) + SourceIndex(0)
+5 >Emitted(50, 36) Source(56, 19) + SourceIndex(0)
 ---
 >>>                };
 1 >^^^^^^^^^^^^^^^^
@@ -868,8 +872,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >		
 2 >                }
-1 >Emitted(47, 17) Source(57, 3) + SourceIndex(0)
-2 >Emitted(47, 18) Source(57, 4) + SourceIndex(0)
+1 >Emitted(51, 17) Source(57, 3) + SourceIndex(0)
+2 >Emitted(51, 18) Source(57, 4) + SourceIndex(0)
 ---
 >>>                FindWidget.prototype.destroy = function () {
 1->^^^^^^^^^^^^^^^^
@@ -880,9 +884,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >		public 
 2 >                destroy
 3 >                                            
-1->Emitted(48, 17) Source(59, 10) + SourceIndex(0)
-2 >Emitted(48, 45) Source(59, 17) + SourceIndex(0)
-3 >Emitted(48, 48) Source(59, 3) + SourceIndex(0)
+1->Emitted(52, 17) Source(59, 10) + SourceIndex(0)
+2 >Emitted(52, 45) Source(59, 17) + SourceIndex(0)
+3 >Emitted(52, 48) Source(59, 3) + SourceIndex(0)
 ---
 >>>                };
 1 >^^^^^^^^^^^^^^^^
@@ -892,8 +896,8 @@ sourceFile:recursiveClassReferenceTest.ts
   >
   >		
 2 >                }
-1 >Emitted(49, 17) Source(61, 3) + SourceIndex(0)
-2 >Emitted(49, 18) Source(61, 4) + SourceIndex(0)
+1 >Emitted(53, 17) Source(61, 3) + SourceIndex(0)
+2 >Emitted(53, 18) Source(61, 4) + SourceIndex(0)
 ---
 >>>                return FindWidget;
 1->^^^^^^^^^^^^^^^^
@@ -902,8 +906,8 @@ sourceFile:recursiveClassReferenceTest.ts
   >
   >	
 2 >                }
-1->Emitted(50, 17) Source(63, 2) + SourceIndex(0)
-2 >Emitted(50, 34) Source(63, 3) + SourceIndex(0)
+1->Emitted(54, 17) Source(63, 2) + SourceIndex(0)
+2 >Emitted(54, 34) Source(63, 3) + SourceIndex(0)
 ---
 >>>            }());
 1 >^^^^^^^^^^^^
@@ -933,10 +937,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >             		}
   >             
   >             	}
-1 >Emitted(51, 13) Source(63, 2) + SourceIndex(0)
-2 >Emitted(51, 14) Source(63, 3) + SourceIndex(0)
-3 >Emitted(51, 14) Source(45, 2) + SourceIndex(0)
-4 >Emitted(51, 18) Source(63, 3) + SourceIndex(0)
+1 >Emitted(55, 13) Source(63, 2) + SourceIndex(0)
+2 >Emitted(55, 14) Source(63, 3) + SourceIndex(0)
+3 >Emitted(55, 14) Source(45, 2) + SourceIndex(0)
+4 >Emitted(55, 18) Source(63, 3) + SourceIndex(0)
 ---
 >>>            Widgets.FindWidget = FindWidget;
 1->^^^^^^^^^^^^
@@ -966,10 +970,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                              
   >                              	}
 4 >                                           
-1->Emitted(52, 13) Source(45, 15) + SourceIndex(0)
-2 >Emitted(52, 31) Source(45, 25) + SourceIndex(0)
-3 >Emitted(52, 44) Source(63, 3) + SourceIndex(0)
-4 >Emitted(52, 45) Source(63, 3) + SourceIndex(0)
+1->Emitted(56, 13) Source(45, 15) + SourceIndex(0)
+2 >Emitted(56, 31) Source(45, 25) + SourceIndex(0)
+3 >Emitted(56, 44) Source(63, 3) + SourceIndex(0)
+4 >Emitted(56, 45) Source(63, 3) + SourceIndex(0)
 ---
 >>>        })(Widgets = Thing.Widgets || (Thing.Widgets = {}));
 1->^^^^^^^^
@@ -1011,15 +1015,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                                    
   >                                                    	}
   >                                                    }
-1->Emitted(53, 9) Source(64, 1) + SourceIndex(0)
-2 >Emitted(53, 10) Source(64, 2) + SourceIndex(0)
-3 >Emitted(53, 12) Source(44, 21) + SourceIndex(0)
-4 >Emitted(53, 19) Source(44, 28) + SourceIndex(0)
-5 >Emitted(53, 22) Source(44, 21) + SourceIndex(0)
-6 >Emitted(53, 35) Source(44, 28) + SourceIndex(0)
-7 >Emitted(53, 40) Source(44, 21) + SourceIndex(0)
-8 >Emitted(53, 53) Source(44, 28) + SourceIndex(0)
-9 >Emitted(53, 61) Source(64, 2) + SourceIndex(0)
+1->Emitted(57, 9) Source(64, 1) + SourceIndex(0)
+2 >Emitted(57, 10) Source(64, 2) + SourceIndex(0)
+3 >Emitted(57, 12) Source(44, 21) + SourceIndex(0)
+4 >Emitted(57, 19) Source(44, 28) + SourceIndex(0)
+5 >Emitted(57, 22) Source(44, 21) + SourceIndex(0)
+6 >Emitted(57, 35) Source(44, 28) + SourceIndex(0)
+7 >Emitted(57, 40) Source(44, 21) + SourceIndex(0)
+8 >Emitted(57, 53) Source(44, 28) + SourceIndex(0)
+9 >Emitted(57, 61) Source(64, 2) + SourceIndex(0)
 ---
 >>>    })(Thing = Sample.Thing || (Sample.Thing = {}));
 1 >^^^^
@@ -1060,15 +1064,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                            
   >                                            	}
   >                                            }
-1 >Emitted(54, 5) Source(64, 1) + SourceIndex(0)
-2 >Emitted(54, 6) Source(64, 2) + SourceIndex(0)
-3 >Emitted(54, 8) Source(44, 15) + SourceIndex(0)
-4 >Emitted(54, 13) Source(44, 20) + SourceIndex(0)
-5 >Emitted(54, 16) Source(44, 15) + SourceIndex(0)
-6 >Emitted(54, 28) Source(44, 20) + SourceIndex(0)
-7 >Emitted(54, 33) Source(44, 15) + SourceIndex(0)
-8 >Emitted(54, 45) Source(44, 20) + SourceIndex(0)
-9 >Emitted(54, 53) Source(64, 2) + SourceIndex(0)
+1 >Emitted(58, 5) Source(64, 1) + SourceIndex(0)
+2 >Emitted(58, 6) Source(64, 2) + SourceIndex(0)
+3 >Emitted(58, 8) Source(44, 15) + SourceIndex(0)
+4 >Emitted(58, 13) Source(44, 20) + SourceIndex(0)
+5 >Emitted(58, 16) Source(44, 15) + SourceIndex(0)
+6 >Emitted(58, 28) Source(44, 20) + SourceIndex(0)
+7 >Emitted(58, 33) Source(44, 15) + SourceIndex(0)
+8 >Emitted(58, 45) Source(44, 20) + SourceIndex(0)
+9 >Emitted(58, 53) Source(64, 2) + SourceIndex(0)
 ---
 >>>})(Sample || (Sample = {}));
 1 >
@@ -1106,13 +1110,13 @@ sourceFile:recursiveClassReferenceTest.ts
   >                    
   >                    	}
   >                    }
-1 >Emitted(55, 1) Source(64, 1) + SourceIndex(0)
-2 >Emitted(55, 2) Source(64, 2) + SourceIndex(0)
-3 >Emitted(55, 4) Source(44, 8) + SourceIndex(0)
-4 >Emitted(55, 10) Source(44, 14) + SourceIndex(0)
-5 >Emitted(55, 15) Source(44, 8) + SourceIndex(0)
-6 >Emitted(55, 21) Source(44, 14) + SourceIndex(0)
-7 >Emitted(55, 29) Source(64, 2) + SourceIndex(0)
+1 >Emitted(59, 1) Source(64, 1) + SourceIndex(0)
+2 >Emitted(59, 2) Source(64, 2) + SourceIndex(0)
+3 >Emitted(59, 4) Source(44, 8) + SourceIndex(0)
+4 >Emitted(59, 10) Source(44, 14) + SourceIndex(0)
+5 >Emitted(59, 15) Source(44, 8) + SourceIndex(0)
+6 >Emitted(59, 21) Source(44, 14) + SourceIndex(0)
+7 >Emitted(59, 29) Source(64, 2) + SourceIndex(0)
 ---
 >>>var AbstractMode = (function () {
 1->
@@ -1121,13 +1125,13 @@ sourceFile:recursiveClassReferenceTest.ts
   >
   >interface IMode { getInitialState(): IState;} 
   >
-1->Emitted(56, 1) Source(67, 1) + SourceIndex(0)
+1->Emitted(60, 1) Source(67, 1) + SourceIndex(0)
 ---
 >>>    function AbstractMode() {
 1->^^^^
 2 >    ^^->
 1->
-1->Emitted(57, 5) Source(67, 1) + SourceIndex(0)
+1->Emitted(61, 5) Source(67, 1) + SourceIndex(0)
 ---
 >>>    }
 1->^^^^
@@ -1135,8 +1139,8 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1->class AbstractMode implements IMode { public getInitialState(): IState { return null;} 
 2 >    }
-1->Emitted(58, 5) Source(67, 88) + SourceIndex(0)
-2 >Emitted(58, 6) Source(67, 89) + SourceIndex(0)
+1->Emitted(62, 5) Source(67, 88) + SourceIndex(0)
+2 >Emitted(62, 6) Source(67, 89) + SourceIndex(0)
 ---
 >>>    AbstractMode.prototype.getInitialState = function () { return null; };
 1->^^^^
@@ -1159,24 +1163,24 @@ sourceFile:recursiveClassReferenceTest.ts
 8 >                                                                      ;
 9 >                                                                       
 10>                                                                        }
-1->Emitted(59, 5) Source(67, 46) + SourceIndex(0)
-2 >Emitted(59, 43) Source(67, 61) + SourceIndex(0)
-3 >Emitted(59, 46) Source(67, 39) + SourceIndex(0)
-4 >Emitted(59, 60) Source(67, 74) + SourceIndex(0)
-5 >Emitted(59, 66) Source(67, 80) + SourceIndex(0)
-6 >Emitted(59, 67) Source(67, 81) + SourceIndex(0)
-7 >Emitted(59, 71) Source(67, 85) + SourceIndex(0)
-8 >Emitted(59, 72) Source(67, 86) + SourceIndex(0)
-9 >Emitted(59, 73) Source(67, 86) + SourceIndex(0)
-10>Emitted(59, 74) Source(67, 87) + SourceIndex(0)
+1->Emitted(63, 5) Source(67, 46) + SourceIndex(0)
+2 >Emitted(63, 43) Source(67, 61) + SourceIndex(0)
+3 >Emitted(63, 46) Source(67, 39) + SourceIndex(0)
+4 >Emitted(63, 60) Source(67, 74) + SourceIndex(0)
+5 >Emitted(63, 66) Source(67, 80) + SourceIndex(0)
+6 >Emitted(63, 67) Source(67, 81) + SourceIndex(0)
+7 >Emitted(63, 71) Source(67, 85) + SourceIndex(0)
+8 >Emitted(63, 72) Source(67, 86) + SourceIndex(0)
+9 >Emitted(63, 73) Source(67, 86) + SourceIndex(0)
+10>Emitted(63, 74) Source(67, 87) + SourceIndex(0)
 ---
 >>>    return AbstractMode;
 1 >^^^^
 2 >    ^^^^^^^^^^^^^^^^^^^
 1 > 
 2 >    }
-1 >Emitted(60, 5) Source(67, 88) + SourceIndex(0)
-2 >Emitted(60, 24) Source(67, 89) + SourceIndex(0)
+1 >Emitted(64, 5) Source(67, 88) + SourceIndex(0)
+2 >Emitted(64, 24) Source(67, 89) + SourceIndex(0)
 ---
 >>>}());
 1 >
@@ -1188,10 +1192,10 @@ sourceFile:recursiveClassReferenceTest.ts
 2 >}
 3 > 
 4 > class AbstractMode implements IMode { public getInitialState(): IState { return null;} }
-1 >Emitted(61, 1) Source(67, 88) + SourceIndex(0)
-2 >Emitted(61, 2) Source(67, 89) + SourceIndex(0)
-3 >Emitted(61, 2) Source(67, 1) + SourceIndex(0)
-4 >Emitted(61, 6) Source(67, 89) + SourceIndex(0)
+1 >Emitted(65, 1) Source(67, 88) + SourceIndex(0)
+2 >Emitted(65, 2) Source(67, 89) + SourceIndex(0)
+3 >Emitted(65, 2) Source(67, 1) + SourceIndex(0)
+4 >Emitted(65, 6) Source(67, 89) + SourceIndex(0)
 ---
 >>>(function (Sample) {
 1->
@@ -1209,9 +1213,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >
 2 >module 
 3 >           Sample
-1->Emitted(62, 1) Source(76, 1) + SourceIndex(0)
-2 >Emitted(62, 12) Source(76, 8) + SourceIndex(0)
-3 >Emitted(62, 18) Source(76, 14) + SourceIndex(0)
+1->Emitted(66, 1) Source(76, 1) + SourceIndex(0)
+2 >Emitted(66, 12) Source(76, 8) + SourceIndex(0)
+3 >Emitted(66, 18) Source(76, 14) + SourceIndex(0)
 ---
 >>>    var Thing;
 1 >^^^^
@@ -1247,10 +1251,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >             
   >             	}
   >             }
-1 >Emitted(63, 5) Source(76, 15) + SourceIndex(0)
-2 >Emitted(63, 9) Source(76, 15) + SourceIndex(0)
-3 >Emitted(63, 14) Source(76, 20) + SourceIndex(0)
-4 >Emitted(63, 15) Source(100, 2) + SourceIndex(0)
+1 >Emitted(67, 5) Source(76, 15) + SourceIndex(0)
+2 >Emitted(67, 9) Source(76, 15) + SourceIndex(0)
+3 >Emitted(67, 14) Source(76, 20) + SourceIndex(0)
+4 >Emitted(67, 15) Source(100, 2) + SourceIndex(0)
 ---
 >>>    (function (Thing) {
 1->^^^^
@@ -1260,9 +1264,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >    
 3 >               Thing
-1->Emitted(64, 5) Source(76, 15) + SourceIndex(0)
-2 >Emitted(64, 16) Source(76, 15) + SourceIndex(0)
-3 >Emitted(64, 21) Source(76, 20) + SourceIndex(0)
+1->Emitted(68, 5) Source(76, 15) + SourceIndex(0)
+2 >Emitted(68, 16) Source(76, 15) + SourceIndex(0)
+3 >Emitted(68, 21) Source(76, 20) + SourceIndex(0)
 ---
 >>>        var Languages;
 1->^^^^^^^^
@@ -1298,10 +1302,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                     
   >                     	}
   >                     }
-1->Emitted(65, 9) Source(76, 21) + SourceIndex(0)
-2 >Emitted(65, 13) Source(76, 21) + SourceIndex(0)
-3 >Emitted(65, 22) Source(76, 30) + SourceIndex(0)
-4 >Emitted(65, 23) Source(100, 2) + SourceIndex(0)
+1->Emitted(69, 9) Source(76, 21) + SourceIndex(0)
+2 >Emitted(69, 13) Source(76, 21) + SourceIndex(0)
+3 >Emitted(69, 22) Source(76, 30) + SourceIndex(0)
+4 >Emitted(69, 23) Source(100, 2) + SourceIndex(0)
 ---
 >>>        (function (Languages) {
 1->^^^^^^^^
@@ -1310,9 +1314,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >        
 3 >                   Languages
-1->Emitted(66, 9) Source(76, 21) + SourceIndex(0)
-2 >Emitted(66, 20) Source(76, 21) + SourceIndex(0)
-3 >Emitted(66, 29) Source(76, 30) + SourceIndex(0)
+1->Emitted(70, 9) Source(76, 21) + SourceIndex(0)
+2 >Emitted(70, 20) Source(76, 21) + SourceIndex(0)
+3 >Emitted(70, 29) Source(76, 30) + SourceIndex(0)
 ---
 >>>            var PlainText;
 1 >^^^^^^^^^^^^
@@ -1348,10 +1352,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                         
   >                         	}
   >                         }
-1 >Emitted(67, 13) Source(76, 31) + SourceIndex(0)
-2 >Emitted(67, 17) Source(76, 31) + SourceIndex(0)
-3 >Emitted(67, 26) Source(76, 40) + SourceIndex(0)
-4 >Emitted(67, 27) Source(100, 2) + SourceIndex(0)
+1 >Emitted(71, 13) Source(76, 31) + SourceIndex(0)
+2 >Emitted(71, 17) Source(76, 31) + SourceIndex(0)
+3 >Emitted(71, 26) Source(76, 40) + SourceIndex(0)
+4 >Emitted(71, 27) Source(100, 2) + SourceIndex(0)
 ---
 >>>            (function (PlainText) {
 1->^^^^^^^^^^^^
@@ -1361,9 +1365,9 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
 2 >            
 3 >                       PlainText
-1->Emitted(68, 13) Source(76, 31) + SourceIndex(0)
-2 >Emitted(68, 24) Source(76, 31) + SourceIndex(0)
-3 >Emitted(68, 33) Source(76, 40) + SourceIndex(0)
+1->Emitted(72, 13) Source(76, 31) + SourceIndex(0)
+2 >Emitted(72, 24) Source(76, 31) + SourceIndex(0)
+3 >Emitted(72, 33) Source(76, 40) + SourceIndex(0)
 ---
 >>>                var State = (function () {
 1->^^^^^^^^^^^^^^^^
@@ -1371,7 +1375,7 @@ sourceFile:recursiveClassReferenceTest.ts
 1-> {
   >	
   >	
-1->Emitted(69, 17) Source(78, 2) + SourceIndex(0)
+1->Emitted(73, 17) Source(78, 2) + SourceIndex(0)
 ---
 >>>                    function State(mode) {
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1382,9 +1386,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >        
 2 >                    constructor(private 
 3 >                                   mode: IMode
-1->Emitted(70, 21) Source(79, 9) + SourceIndex(0)
-2 >Emitted(70, 36) Source(79, 29) + SourceIndex(0)
-3 >Emitted(70, 40) Source(79, 40) + SourceIndex(0)
+1->Emitted(74, 21) Source(79, 9) + SourceIndex(0)
+2 >Emitted(74, 36) Source(79, 29) + SourceIndex(0)
+3 >Emitted(74, 40) Source(79, 40) + SourceIndex(0)
 ---
 >>>                        this.mode = mode;
 1->^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1397,11 +1401,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                                 
 4 >                                    mode
 5 >                                        : IMode
-1->Emitted(71, 25) Source(79, 29) + SourceIndex(0)
-2 >Emitted(71, 34) Source(79, 33) + SourceIndex(0)
-3 >Emitted(71, 37) Source(79, 29) + SourceIndex(0)
-4 >Emitted(71, 41) Source(79, 33) + SourceIndex(0)
-5 >Emitted(71, 42) Source(79, 40) + SourceIndex(0)
+1->Emitted(75, 25) Source(79, 29) + SourceIndex(0)
+2 >Emitted(75, 34) Source(79, 33) + SourceIndex(0)
+3 >Emitted(75, 37) Source(79, 29) + SourceIndex(0)
+4 >Emitted(75, 41) Source(79, 33) + SourceIndex(0)
+5 >Emitted(75, 42) Source(79, 40) + SourceIndex(0)
 ---
 >>>                    }
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -1409,8 +1413,8 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >) { 
 2 >                    }
-1 >Emitted(72, 21) Source(79, 44) + SourceIndex(0)
-2 >Emitted(72, 22) Source(79, 45) + SourceIndex(0)
+1 >Emitted(76, 21) Source(79, 44) + SourceIndex(0)
+2 >Emitted(76, 22) Source(79, 45) + SourceIndex(0)
 ---
 >>>                    State.prototype.clone = function () {
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1420,9 +1424,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >		public 
 2 >                    clone
 3 >                                         
-1->Emitted(73, 21) Source(80, 10) + SourceIndex(0)
-2 >Emitted(73, 42) Source(80, 15) + SourceIndex(0)
-3 >Emitted(73, 45) Source(80, 3) + SourceIndex(0)
+1->Emitted(77, 21) Source(80, 10) + SourceIndex(0)
+2 >Emitted(77, 42) Source(80, 15) + SourceIndex(0)
+3 >Emitted(77, 45) Source(80, 3) + SourceIndex(0)
 ---
 >>>                        return this;
 1 >^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1436,11 +1440,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                               
 4 >                               this
 5 >                                   ;
-1 >Emitted(74, 25) Source(81, 4) + SourceIndex(0)
-2 >Emitted(74, 31) Source(81, 10) + SourceIndex(0)
-3 >Emitted(74, 32) Source(81, 11) + SourceIndex(0)
-4 >Emitted(74, 36) Source(81, 15) + SourceIndex(0)
-5 >Emitted(74, 37) Source(81, 16) + SourceIndex(0)
+1 >Emitted(78, 25) Source(81, 4) + SourceIndex(0)
+2 >Emitted(78, 31) Source(81, 10) + SourceIndex(0)
+3 >Emitted(78, 32) Source(81, 11) + SourceIndex(0)
+4 >Emitted(78, 36) Source(81, 15) + SourceIndex(0)
+5 >Emitted(78, 37) Source(81, 16) + SourceIndex(0)
 ---
 >>>                    };
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -1449,8 +1453,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >		
 2 >                    }
-1 >Emitted(75, 21) Source(82, 3) + SourceIndex(0)
-2 >Emitted(75, 22) Source(82, 4) + SourceIndex(0)
+1 >Emitted(79, 21) Source(82, 3) + SourceIndex(0)
+2 >Emitted(79, 22) Source(82, 4) + SourceIndex(0)
 ---
 >>>                    State.prototype.equals = function (other) {
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1465,11 +1469,11 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                                          
 4 >                                             public equals(
 5 >                                                       other:IState
-1->Emitted(76, 21) Source(84, 10) + SourceIndex(0)
-2 >Emitted(76, 43) Source(84, 16) + SourceIndex(0)
-3 >Emitted(76, 46) Source(84, 3) + SourceIndex(0)
-4 >Emitted(76, 56) Source(84, 17) + SourceIndex(0)
-5 >Emitted(76, 61) Source(84, 29) + SourceIndex(0)
+1->Emitted(80, 21) Source(84, 10) + SourceIndex(0)
+2 >Emitted(80, 43) Source(84, 16) + SourceIndex(0)
+3 >Emitted(80, 46) Source(84, 3) + SourceIndex(0)
+4 >Emitted(80, 56) Source(84, 17) + SourceIndex(0)
+5 >Emitted(80, 61) Source(84, 29) + SourceIndex(0)
 ---
 >>>                        return this === other;
 1 >^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1487,13 +1491,13 @@ sourceFile:recursiveClassReferenceTest.ts
 5 >                                    === 
 6 >                                        other
 7 >                                             ;
-1 >Emitted(77, 25) Source(85, 4) + SourceIndex(0)
-2 >Emitted(77, 31) Source(85, 10) + SourceIndex(0)
-3 >Emitted(77, 32) Source(85, 11) + SourceIndex(0)
-4 >Emitted(77, 36) Source(85, 15) + SourceIndex(0)
-5 >Emitted(77, 41) Source(85, 20) + SourceIndex(0)
-6 >Emitted(77, 46) Source(85, 25) + SourceIndex(0)
-7 >Emitted(77, 47) Source(85, 26) + SourceIndex(0)
+1 >Emitted(81, 25) Source(85, 4) + SourceIndex(0)
+2 >Emitted(81, 31) Source(85, 10) + SourceIndex(0)
+3 >Emitted(81, 32) Source(85, 11) + SourceIndex(0)
+4 >Emitted(81, 36) Source(85, 15) + SourceIndex(0)
+5 >Emitted(81, 41) Source(85, 20) + SourceIndex(0)
+6 >Emitted(81, 46) Source(85, 25) + SourceIndex(0)
+7 >Emitted(81, 47) Source(85, 26) + SourceIndex(0)
 ---
 >>>                    };
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -1502,8 +1506,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >		
 2 >                    }
-1 >Emitted(78, 21) Source(86, 3) + SourceIndex(0)
-2 >Emitted(78, 22) Source(86, 4) + SourceIndex(0)
+1 >Emitted(82, 21) Source(86, 3) + SourceIndex(0)
+2 >Emitted(82, 22) Source(86, 4) + SourceIndex(0)
 ---
 >>>                    State.prototype.getMode = function () { return mode; };
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1528,16 +1532,16 @@ sourceFile:recursiveClassReferenceTest.ts
 8 >                                                                       ;
 9 >                                                                         
 10>                                                                         }
-1->Emitted(79, 21) Source(88, 10) + SourceIndex(0)
-2 >Emitted(79, 44) Source(88, 17) + SourceIndex(0)
-3 >Emitted(79, 47) Source(88, 3) + SourceIndex(0)
-4 >Emitted(79, 61) Source(88, 29) + SourceIndex(0)
-5 >Emitted(79, 67) Source(88, 35) + SourceIndex(0)
-6 >Emitted(79, 68) Source(88, 36) + SourceIndex(0)
-7 >Emitted(79, 72) Source(88, 40) + SourceIndex(0)
-8 >Emitted(79, 73) Source(88, 41) + SourceIndex(0)
-9 >Emitted(79, 74) Source(88, 42) + SourceIndex(0)
-10>Emitted(79, 75) Source(88, 43) + SourceIndex(0)
+1->Emitted(83, 21) Source(88, 10) + SourceIndex(0)
+2 >Emitted(83, 44) Source(88, 17) + SourceIndex(0)
+3 >Emitted(83, 47) Source(88, 3) + SourceIndex(0)
+4 >Emitted(83, 61) Source(88, 29) + SourceIndex(0)
+5 >Emitted(83, 67) Source(88, 35) + SourceIndex(0)
+6 >Emitted(83, 68) Source(88, 36) + SourceIndex(0)
+7 >Emitted(83, 72) Source(88, 40) + SourceIndex(0)
+8 >Emitted(83, 73) Source(88, 41) + SourceIndex(0)
+9 >Emitted(83, 74) Source(88, 42) + SourceIndex(0)
+10>Emitted(83, 75) Source(88, 43) + SourceIndex(0)
 ---
 >>>                    return State;
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -1545,8 +1549,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >	
 2 >                    }
-1 >Emitted(80, 21) Source(89, 2) + SourceIndex(0)
-2 >Emitted(80, 33) Source(89, 3) + SourceIndex(0)
+1 >Emitted(84, 21) Source(89, 2) + SourceIndex(0)
+2 >Emitted(84, 33) Source(89, 3) + SourceIndex(0)
 ---
 >>>                }());
 1 >^^^^^^^^^^^^^^^^
@@ -1569,10 +1573,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                 		
   >                 		public getMode(): IMode { return mode; }
   >                 	}
-1 >Emitted(81, 17) Source(89, 2) + SourceIndex(0)
-2 >Emitted(81, 18) Source(89, 3) + SourceIndex(0)
-3 >Emitted(81, 18) Source(78, 2) + SourceIndex(0)
-4 >Emitted(81, 22) Source(89, 3) + SourceIndex(0)
+1 >Emitted(85, 17) Source(89, 2) + SourceIndex(0)
+2 >Emitted(85, 18) Source(89, 3) + SourceIndex(0)
+3 >Emitted(85, 18) Source(78, 2) + SourceIndex(0)
+4 >Emitted(85, 22) Source(89, 3) + SourceIndex(0)
 ---
 >>>                PlainText.State = State;
 1->^^^^^^^^^^^^^^^^
@@ -1595,10 +1599,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                               		public getMode(): IMode { return mode; }
   >                               	}
 4 >                                       
-1->Emitted(82, 17) Source(78, 15) + SourceIndex(0)
-2 >Emitted(82, 32) Source(78, 20) + SourceIndex(0)
-3 >Emitted(82, 40) Source(89, 3) + SourceIndex(0)
-4 >Emitted(82, 41) Source(89, 3) + SourceIndex(0)
+1->Emitted(86, 17) Source(78, 15) + SourceIndex(0)
+2 >Emitted(86, 32) Source(78, 20) + SourceIndex(0)
+3 >Emitted(86, 40) Source(89, 3) + SourceIndex(0)
+4 >Emitted(86, 41) Source(89, 3) + SourceIndex(0)
 ---
 >>>                var Mode = (function (_super) {
 1->^^^^^^^^^^^^^^^^
@@ -1606,21 +1610,21 @@ sourceFile:recursiveClassReferenceTest.ts
 1->
   >	
   >	
-1->Emitted(83, 17) Source(91, 2) + SourceIndex(0)
+1->Emitted(87, 17) Source(91, 2) + SourceIndex(0)
 ---
 >>>                    __extends(Mode, _super);
 1->^^^^^^^^^^^^^^^^^^^^
 2 >                    ^^^^^^^^^^^^^^^^^^^^^^^^
 1->export class Mode extends 
 2 >                    AbstractMode
-1->Emitted(84, 21) Source(91, 28) + SourceIndex(0)
-2 >Emitted(84, 45) Source(91, 40) + SourceIndex(0)
+1->Emitted(88, 21) Source(91, 28) + SourceIndex(0)
+2 >Emitted(88, 45) Source(91, 40) + SourceIndex(0)
 ---
 >>>                    function Mode() {
 1 >^^^^^^^^^^^^^^^^^^^^
 2 >                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
-1 >Emitted(85, 21) Source(91, 2) + SourceIndex(0)
+1 >Emitted(89, 21) Source(91, 2) + SourceIndex(0)
 ---
 >>>                        return _super.apply(this, arguments) || this;
 >>>                    }
@@ -1637,8 +1641,8 @@ sourceFile:recursiveClassReferenceTest.ts
   >
   >	
 2 >                    }
-1->Emitted(87, 21) Source(99, 2) + SourceIndex(0)
-2 >Emitted(87, 22) Source(99, 3) + SourceIndex(0)
+1->Emitted(91, 21) Source(99, 2) + SourceIndex(0)
+2 >Emitted(91, 22) Source(99, 3) + SourceIndex(0)
 ---
 >>>                    // scenario 2
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1646,8 +1650,8 @@ sourceFile:recursiveClassReferenceTest.ts
 3 >                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1->
 2 >                    // scenario 2
-1->Emitted(88, 21) Source(93, 3) + SourceIndex(0)
-2 >Emitted(88, 34) Source(93, 16) + SourceIndex(0)
+1->Emitted(92, 21) Source(93, 3) + SourceIndex(0)
+2 >Emitted(92, 34) Source(93, 16) + SourceIndex(0)
 ---
 >>>                    Mode.prototype.getInitialState = function () {
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1657,9 +1661,9 @@ sourceFile:recursiveClassReferenceTest.ts
   >		public 
 2 >                    getInitialState
 3 >                                                  
-1->Emitted(89, 21) Source(94, 10) + SourceIndex(0)
-2 >Emitted(89, 51) Source(94, 25) + SourceIndex(0)
-3 >Emitted(89, 54) Source(94, 3) + SourceIndex(0)
+1->Emitted(93, 21) Source(94, 10) + SourceIndex(0)
+2 >Emitted(93, 51) Source(94, 25) + SourceIndex(0)
+3 >Emitted(93, 54) Source(94, 3) + SourceIndex(0)
 ---
 >>>                        return new State(self);
 1 >^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1681,15 +1685,15 @@ sourceFile:recursiveClassReferenceTest.ts
 7 >                                         self
 8 >                                             )
 9 >                                              ;
-1 >Emitted(90, 25) Source(95, 4) + SourceIndex(0)
-2 >Emitted(90, 31) Source(95, 10) + SourceIndex(0)
-3 >Emitted(90, 32) Source(95, 11) + SourceIndex(0)
-4 >Emitted(90, 36) Source(95, 15) + SourceIndex(0)
-5 >Emitted(90, 41) Source(95, 20) + SourceIndex(0)
-6 >Emitted(90, 42) Source(95, 21) + SourceIndex(0)
-7 >Emitted(90, 46) Source(95, 25) + SourceIndex(0)
-8 >Emitted(90, 47) Source(95, 26) + SourceIndex(0)
-9 >Emitted(90, 48) Source(95, 27) + SourceIndex(0)
+1 >Emitted(94, 25) Source(95, 4) + SourceIndex(0)
+2 >Emitted(94, 31) Source(95, 10) + SourceIndex(0)
+3 >Emitted(94, 32) Source(95, 11) + SourceIndex(0)
+4 >Emitted(94, 36) Source(95, 15) + SourceIndex(0)
+5 >Emitted(94, 41) Source(95, 20) + SourceIndex(0)
+6 >Emitted(94, 42) Source(95, 21) + SourceIndex(0)
+7 >Emitted(94, 46) Source(95, 25) + SourceIndex(0)
+8 >Emitted(94, 47) Source(95, 26) + SourceIndex(0)
+9 >Emitted(94, 48) Source(95, 27) + SourceIndex(0)
 ---
 >>>                    };
 1 >^^^^^^^^^^^^^^^^^^^^
@@ -1698,8 +1702,8 @@ sourceFile:recursiveClassReferenceTest.ts
 1 >
   >		
 2 >                    }
-1 >Emitted(91, 21) Source(96, 3) + SourceIndex(0)
-2 >Emitted(91, 22) Source(96, 4) + SourceIndex(0)
+1 >Emitted(95, 21) Source(96, 3) + SourceIndex(0)
+2 >Emitted(95, 22) Source(96, 4) + SourceIndex(0)
 ---
 >>>                    return Mode;
 1->^^^^^^^^^^^^^^^^^^^^
@@ -1710,8 +1714,8 @@ sourceFile:recursiveClassReferenceTest.ts
   >
   >	
 2 >                    }
-1->Emitted(92, 21) Source(99, 2) + SourceIndex(0)
-2 >Emitted(92, 32) Source(99, 3) + SourceIndex(0)
+1->Emitted(96, 21) Source(99, 2) + SourceIndex(0)
+2 >Emitted(96, 32) Source(99, 3) + SourceIndex(0)
 ---
 >>>                }(AbstractMode));
 1->^^^^^^^^^^^^^^^^
@@ -1735,12 +1739,12 @@ sourceFile:recursiveClassReferenceTest.ts
   >                              
   >                              
   >                              	}
-1->Emitted(93, 17) Source(99, 2) + SourceIndex(0)
-2 >Emitted(93, 18) Source(99, 3) + SourceIndex(0)
-3 >Emitted(93, 18) Source(91, 2) + SourceIndex(0)
-4 >Emitted(93, 19) Source(91, 28) + SourceIndex(0)
-5 >Emitted(93, 31) Source(91, 40) + SourceIndex(0)
-6 >Emitted(93, 34) Source(99, 3) + SourceIndex(0)
+1->Emitted(97, 17) Source(99, 2) + SourceIndex(0)
+2 >Emitted(97, 18) Source(99, 3) + SourceIndex(0)
+3 >Emitted(97, 18) Source(91, 2) + SourceIndex(0)
+4 >Emitted(97, 19) Source(91, 28) + SourceIndex(0)
+5 >Emitted(97, 31) Source(91, 40) + SourceIndex(0)
+6 >Emitted(97, 34) Source(99, 3) + SourceIndex(0)
 ---
 >>>                PlainText.Mode = Mode;
 1->^^^^^^^^^^^^^^^^
@@ -1760,10 +1764,10 @@ sourceFile:recursiveClassReferenceTest.ts
   >                              
   >                              	}
 4 >                                     
-1->Emitted(94, 17) Source(91, 15) + SourceIndex(0)
-2 >Emitted(94, 31) Source(91, 19) + SourceIndex(0)
-3 >Emitted(94, 38) Source(99, 3) + SourceIndex(0)
-4 >Emitted(94, 39) Source(99, 3) + SourceIndex(0)
+1->Emitted(98, 17) Source(91, 15) + SourceIndex(0)
+2 >Emitted(98, 31) Source(91, 19) + SourceIndex(0)
+3 >Emitted(98, 38) Source(99, 3) + SourceIndex(0)
+4 >Emitted(98, 39) Source(99, 3) + SourceIndex(0)
 ---
 >>>            })(PlainText = Languages.PlainText || (Languages.PlainText = {}));
 1->^^^^^^^^^^^^
@@ -1809,15 +1813,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                                                      
   >                                                                      	}
   >                                                                      }
-1->Emitted(95, 13) Source(100, 1) + SourceIndex(0)
-2 >Emitted(95, 14) Source(100, 2) + SourceIndex(0)
-3 >Emitted(95, 16) Source(76, 31) + SourceIndex(0)
-4 >Emitted(95, 25) Source(76, 40) + SourceIndex(0)
-5 >Emitted(95, 28) Source(76, 31) + SourceIndex(0)
-6 >Emitted(95, 47) Source(76, 40) + SourceIndex(0)
-7 >Emitted(95, 52) Source(76, 31) + SourceIndex(0)
-8 >Emitted(95, 71) Source(76, 40) + SourceIndex(0)
-9 >Emitted(95, 79) Source(100, 2) + SourceIndex(0)
+1->Emitted(99, 13) Source(100, 1) + SourceIndex(0)
+2 >Emitted(99, 14) Source(100, 2) + SourceIndex(0)
+3 >Emitted(99, 16) Source(76, 31) + SourceIndex(0)
+4 >Emitted(99, 25) Source(76, 40) + SourceIndex(0)
+5 >Emitted(99, 28) Source(76, 31) + SourceIndex(0)
+6 >Emitted(99, 47) Source(76, 40) + SourceIndex(0)
+7 >Emitted(99, 52) Source(76, 31) + SourceIndex(0)
+8 >Emitted(99, 71) Source(76, 40) + SourceIndex(0)
+9 >Emitted(99, 79) Source(100, 2) + SourceIndex(0)
 ---
 >>>        })(Languages = Thing.Languages || (Thing.Languages = {}));
 1 >^^^^^^^^
@@ -1862,15 +1866,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                                          
   >                                                          	}
   >                                                          }
-1 >Emitted(96, 9) Source(100, 1) + SourceIndex(0)
-2 >Emitted(96, 10) Source(100, 2) + SourceIndex(0)
-3 >Emitted(96, 12) Source(76, 21) + SourceIndex(0)
-4 >Emitted(96, 21) Source(76, 30) + SourceIndex(0)
-5 >Emitted(96, 24) Source(76, 21) + SourceIndex(0)
-6 >Emitted(96, 39) Source(76, 30) + SourceIndex(0)
-7 >Emitted(96, 44) Source(76, 21) + SourceIndex(0)
-8 >Emitted(96, 59) Source(76, 30) + SourceIndex(0)
-9 >Emitted(96, 67) Source(100, 2) + SourceIndex(0)
+1 >Emitted(100, 9) Source(100, 1) + SourceIndex(0)
+2 >Emitted(100, 10) Source(100, 2) + SourceIndex(0)
+3 >Emitted(100, 12) Source(76, 21) + SourceIndex(0)
+4 >Emitted(100, 21) Source(76, 30) + SourceIndex(0)
+5 >Emitted(100, 24) Source(76, 21) + SourceIndex(0)
+6 >Emitted(100, 39) Source(76, 30) + SourceIndex(0)
+7 >Emitted(100, 44) Source(76, 21) + SourceIndex(0)
+8 >Emitted(100, 59) Source(76, 30) + SourceIndex(0)
+9 >Emitted(100, 67) Source(100, 2) + SourceIndex(0)
 ---
 >>>    })(Thing = Sample.Thing || (Sample.Thing = {}));
 1 >^^^^
@@ -1915,15 +1919,15 @@ sourceFile:recursiveClassReferenceTest.ts
   >                                            
   >                                            	}
   >                                            }
-1 >Emitted(97, 5) Source(100, 1) + SourceIndex(0)
-2 >Emitted(97, 6) Source(100, 2) + SourceIndex(0)
-3 >Emitted(97, 8) Source(76, 15) + SourceIndex(0)
-4 >Emitted(97, 13) Source(76, 20) + SourceIndex(0)
-5 >Emitted(97, 16) Source(76, 15) + SourceIndex(0)
-6 >Emitted(97, 28) Source(76, 20) + SourceIndex(0)
-7 >Emitted(97, 33) Source(76, 15) + SourceIndex(0)
-8 >Emitted(97, 45) Source(76, 20) + SourceIndex(0)
-9 >Emitted(97, 53) Source(100, 2) + SourceIndex(0)
+1 >Emitted(101, 5) Source(100, 1) + SourceIndex(0)
+2 >Emitted(101, 6) Source(100, 2) + SourceIndex(0)
+3 >Emitted(101, 8) Source(76, 15) + SourceIndex(0)
+4 >Emitted(101, 13) Source(76, 20) + SourceIndex(0)
+5 >Emitted(101, 16) Source(76, 15) + SourceIndex(0)
+6 >Emitted(101, 28) Source(76, 20) + SourceIndex(0)
+7 >Emitted(101, 33) Source(76, 15) + SourceIndex(0)
+8 >Emitted(101, 45) Source(76, 20) + SourceIndex(0)
+9 >Emitted(101, 53) Source(100, 2) + SourceIndex(0)
 ---
 >>>})(Sample || (Sample = {}));
 1 >
@@ -1965,12 +1969,12 @@ sourceFile:recursiveClassReferenceTest.ts
   >                    
   >                    	}
   >                    }
-1 >Emitted(98, 1) Source(100, 1) + SourceIndex(0)
-2 >Emitted(98, 2) Source(100, 2) + SourceIndex(0)
-3 >Emitted(98, 4) Source(76, 8) + SourceIndex(0)
-4 >Emitted(98, 10) Source(76, 14) + SourceIndex(0)
-5 >Emitted(98, 15) Source(76, 8) + SourceIndex(0)
-6 >Emitted(98, 21) Source(76, 14) + SourceIndex(0)
-7 >Emitted(98, 29) Source(100, 2) + SourceIndex(0)
+1 >Emitted(102, 1) Source(100, 1) + SourceIndex(0)
+2 >Emitted(102, 2) Source(100, 2) + SourceIndex(0)
+3 >Emitted(102, 4) Source(76, 8) + SourceIndex(0)
+4 >Emitted(102, 10) Source(76, 14) + SourceIndex(0)
+5 >Emitted(102, 15) Source(76, 8) + SourceIndex(0)
+6 >Emitted(102, 21) Source(76, 14) + SourceIndex(0)
+7 >Emitted(102, 29) Source(100, 2) + SourceIndex(0)
 ---
 >>>//# sourceMappingURL=recursiveClassReferenceTest.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/recursiveComplicatedClasses.js b/tests/baselines/reference/recursiveComplicatedClasses.js
index 57000180db4..c9b3dfb6d7a 100644
--- a/tests/baselines/reference/recursiveComplicatedClasses.js
+++ b/tests/baselines/reference/recursiveComplicatedClasses.js
@@ -26,7 +26,11 @@ class TypeSymbol extends InferenceSymbol {
 
 //// [recursiveComplicatedClasses.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js b/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js
index 5f6e3ab0b06..e7ce63794fd 100644
--- a/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js
+++ b/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js
@@ -31,7 +31,11 @@ declare module MsPortal.Controls.Base.ItemList {
 
 //// [recursivelySpecializedConstructorDeclaration.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/reexportClassDefinition.js b/tests/baselines/reference/reexportClassDefinition.js
index d7b644514cc..37ba6aab5d4 100644
--- a/tests/baselines/reference/reexportClassDefinition.js
+++ b/tests/baselines/reference/reexportClassDefinition.js
@@ -34,7 +34,11 @@ module.exports = {
 //// [foo3.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/resolvingClassDeclarationWhenInBaseTypeResolution.js b/tests/baselines/reference/resolvingClassDeclarationWhenInBaseTypeResolution.js
index 77417da53f3..d81c9a0e2a7 100644
--- a/tests/baselines/reference/resolvingClassDeclarationWhenInBaseTypeResolution.js
+++ b/tests/baselines/reference/resolvingClassDeclarationWhenInBaseTypeResolution.js
@@ -1021,7 +1021,11 @@ module caurinus {
 
 //// [resolvingClassDeclarationWhenInBaseTypeResolution.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/returnInConstructor1.js b/tests/baselines/reference/returnInConstructor1.js
index cd56b78f0a3..2f2c4a3fdb5 100644
--- a/tests/baselines/reference/returnInConstructor1.js
+++ b/tests/baselines/reference/returnInConstructor1.js
@@ -68,7 +68,11 @@ class I extends G {
 
 //// [returnInConstructor1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/returnStatements.js b/tests/baselines/reference/returnStatements.js
index 783ffb5899e..3488ebd8ac0 100644
--- a/tests/baselines/reference/returnStatements.js
+++ b/tests/baselines/reference/returnStatements.js
@@ -26,7 +26,11 @@ function fn13(): C { return null; }
 
 //// [returnStatements.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.js b/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.js
index 1ab4b160e7c..67013c3922e 100644
--- a/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.js
+++ b/tests/baselines/reference/scopeCheckExtendedClassInsidePublicMethod2.js
@@ -10,7 +10,11 @@ class D extends C {
 
 //// [scopeCheckExtendedClassInsidePublicMethod2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.js b/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.js
index 9d1fafea4c9..7bb90a136ba 100644
--- a/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.js
+++ b/tests/baselines/reference/scopeCheckExtendedClassInsideStaticMethod1.js
@@ -10,7 +10,11 @@ class D extends C {
 
 //// [scopeCheckExtendedClassInsideStaticMethod1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/scopeTests.js b/tests/baselines/reference/scopeTests.js
index 0ab152adf11..d2061241cac 100644
--- a/tests/baselines/reference/scopeTests.js
+++ b/tests/baselines/reference/scopeTests.js
@@ -13,7 +13,11 @@ class D extends C {
 
 //// [scopeTests.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/shadowPrivateMembers.js b/tests/baselines/reference/shadowPrivateMembers.js
index 305c7581959..251622f1308 100644
--- a/tests/baselines/reference/shadowPrivateMembers.js
+++ b/tests/baselines/reference/shadowPrivateMembers.js
@@ -5,7 +5,11 @@ class derived extends base { private n() {} }
 
 //// [shadowPrivateMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js b/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js
index d3ac854d4dd..07be6489141 100644
--- a/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js
+++ b/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js
@@ -9,7 +9,11 @@ class Greeter extends AbstractGreeter {
 
 //// [sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js.map b/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js.map
index 6b18a783dfa..27577a7e338 100644
--- a/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js.map
+++ b/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js.map
@@ -1,2 +1,2 @@
 //// [sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js.map]
-{"version":3,"file":"sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js","sourceRoot":"","sources":["sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts"],"names":[],"mappings":";;;;;AAAA;IAAA;IACA,CAAC;IAAD,sBAAC;AAAD,CAAC,AADD,IACC;AAED;IAAsB,2BAAe;IAArC;QAAA,kDAGC;QAFU,OAAC,GAAG,EAAE,CAAC;QACP,WAAK,GAAG,KAAK,CAAC;;IACzB,CAAC;IAAD,cAAC;AAAD,CAAC,AAHD,CAAsB,eAAe,GAGpC"}
\ No newline at end of file
+{"version":3,"file":"sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js","sourceRoot":"","sources":["sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts"],"names":[],"mappings":";;;;;;;;;AAAA;IAAA;IACA,CAAC;IAAD,sBAAC;AAAD,CAAC,AADD,IACC;AAED;IAAsB,2BAAe;IAArC;QAAA,kDAGC;QAFU,OAAC,GAAG,EAAE,CAAC;QACP,WAAK,GAAG,KAAK,CAAC;;IACzB,CAAC;IAAD,cAAC;AAAD,CAAC,AAHD,CAAsB,eAAe,GAGpC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.sourcemap.txt b/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.sourcemap.txt
index 68dea53e96b..cb083f766e8 100644
--- a/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapValidationClassWithDefaultConstructorAndExtendsClause.sourcemap.txt
@@ -9,7 +9,11 @@ emittedFile:tests/cases/compiler/sourceMapValidationClassWithDefaultConstructorA
 sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 -------------------------------------------------------------------
 >>>var __extends = (this && this.__extends) || function (d, b) {
->>>    Object.setPrototypeOf(d, b);
+>>>    if (typeof Object.setPrototypeOf === "function") {
+>>>        Object.setPrototypeOf(d, b);
+>>>    } else {
+>>>        d.__proto__ = b;
+>>>    }
 >>>    function __() { this.constructor = d; }
 >>>    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 >>>};
@@ -17,13 +21,13 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 1 >
 2 >^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
-1 >Emitted(6, 1) Source(1, 1) + SourceIndex(0)
+1 >Emitted(10, 1) Source(1, 1) + SourceIndex(0)
 ---
 >>>    function AbstractGreeter() {
 1->^^^^
 2 >    ^^->
 1->
-1->Emitted(7, 5) Source(1, 1) + SourceIndex(0)
+1->Emitted(11, 5) Source(1, 1) + SourceIndex(0)
 ---
 >>>    }
 1->^^^^
@@ -32,16 +36,16 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 1->class AbstractGreeter {
   >
 2 >    }
-1->Emitted(8, 5) Source(2, 1) + SourceIndex(0)
-2 >Emitted(8, 6) Source(2, 2) + SourceIndex(0)
+1->Emitted(12, 5) Source(2, 1) + SourceIndex(0)
+2 >Emitted(12, 6) Source(2, 2) + SourceIndex(0)
 ---
 >>>    return AbstractGreeter;
 1->^^^^
 2 >    ^^^^^^^^^^^^^^^^^^^^^^
 1->
 2 >    }
-1->Emitted(9, 5) Source(2, 1) + SourceIndex(0)
-2 >Emitted(9, 27) Source(2, 2) + SourceIndex(0)
+1->Emitted(13, 5) Source(2, 1) + SourceIndex(0)
+2 >Emitted(13, 27) Source(2, 2) + SourceIndex(0)
 ---
 >>>}());
 1 >
@@ -54,10 +58,10 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 3 > 
 4 > class AbstractGreeter {
   > }
-1 >Emitted(10, 1) Source(2, 1) + SourceIndex(0)
-2 >Emitted(10, 2) Source(2, 2) + SourceIndex(0)
-3 >Emitted(10, 2) Source(1, 1) + SourceIndex(0)
-4 >Emitted(10, 6) Source(2, 2) + SourceIndex(0)
+1 >Emitted(14, 1) Source(2, 1) + SourceIndex(0)
+2 >Emitted(14, 2) Source(2, 2) + SourceIndex(0)
+3 >Emitted(14, 2) Source(1, 1) + SourceIndex(0)
+4 >Emitted(14, 6) Source(2, 2) + SourceIndex(0)
 ---
 >>>var Greeter = (function (_super) {
 1->
@@ -65,21 +69,21 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 1->
   >
   >
-1->Emitted(11, 1) Source(4, 1) + SourceIndex(0)
+1->Emitted(15, 1) Source(4, 1) + SourceIndex(0)
 ---
 >>>    __extends(Greeter, _super);
 1->^^^^
 2 >    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 1->class Greeter extends 
 2 >    AbstractGreeter
-1->Emitted(12, 5) Source(4, 23) + SourceIndex(0)
-2 >Emitted(12, 32) Source(4, 38) + SourceIndex(0)
+1->Emitted(16, 5) Source(4, 23) + SourceIndex(0)
+2 >Emitted(16, 32) Source(4, 38) + SourceIndex(0)
 ---
 >>>    function Greeter() {
 1 >^^^^
 2 >    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
-1 >Emitted(13, 5) Source(4, 1) + SourceIndex(0)
+1 >Emitted(17, 5) Source(4, 1) + SourceIndex(0)
 ---
 >>>        var _this = _super.apply(this, arguments) || this;
 1->^^^^^^^^
@@ -89,8 +93,8 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
   >            public a = 10;
   >            public nameA = "Ten";
   >        }
-1->Emitted(14, 9) Source(4, 1) + SourceIndex(0)
-2 >Emitted(14, 59) Source(7, 2) + SourceIndex(0)
+1->Emitted(18, 9) Source(4, 1) + SourceIndex(0)
+2 >Emitted(18, 59) Source(7, 2) + SourceIndex(0)
 ---
 >>>        _this.a = 10;
 1 >^^^^^^^^
@@ -104,11 +108,11 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 3 >                = 
 4 >                  10
 5 >                    ;
-1 >Emitted(15, 9) Source(5, 12) + SourceIndex(0)
-2 >Emitted(15, 16) Source(5, 13) + SourceIndex(0)
-3 >Emitted(15, 19) Source(5, 16) + SourceIndex(0)
-4 >Emitted(15, 21) Source(5, 18) + SourceIndex(0)
-5 >Emitted(15, 22) Source(5, 19) + SourceIndex(0)
+1 >Emitted(19, 9) Source(5, 12) + SourceIndex(0)
+2 >Emitted(19, 16) Source(5, 13) + SourceIndex(0)
+3 >Emitted(19, 19) Source(5, 16) + SourceIndex(0)
+4 >Emitted(19, 21) Source(5, 18) + SourceIndex(0)
+5 >Emitted(19, 22) Source(5, 19) + SourceIndex(0)
 ---
 >>>        _this.nameA = "Ten";
 1->^^^^^^^^
@@ -122,11 +126,11 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 3 >                    = 
 4 >                      "Ten"
 5 >                           ;
-1->Emitted(16, 9) Source(6, 12) + SourceIndex(0)
-2 >Emitted(16, 20) Source(6, 17) + SourceIndex(0)
-3 >Emitted(16, 23) Source(6, 20) + SourceIndex(0)
-4 >Emitted(16, 28) Source(6, 25) + SourceIndex(0)
-5 >Emitted(16, 29) Source(6, 26) + SourceIndex(0)
+1->Emitted(20, 9) Source(6, 12) + SourceIndex(0)
+2 >Emitted(20, 20) Source(6, 17) + SourceIndex(0)
+3 >Emitted(20, 23) Source(6, 20) + SourceIndex(0)
+4 >Emitted(20, 28) Source(6, 25) + SourceIndex(0)
+5 >Emitted(20, 29) Source(6, 26) + SourceIndex(0)
 ---
 >>>        return _this;
 >>>    }
@@ -136,8 +140,8 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 1 >
   >
 2 >    }
-1 >Emitted(18, 5) Source(7, 1) + SourceIndex(0)
-2 >Emitted(18, 6) Source(7, 2) + SourceIndex(0)
+1 >Emitted(22, 5) Source(7, 1) + SourceIndex(0)
+2 >Emitted(22, 6) Source(7, 2) + SourceIndex(0)
 ---
 >>>    return Greeter;
 1->^^^^
@@ -145,8 +149,8 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
 3 >                  ^^^->
 1->
 2 >    }
-1->Emitted(19, 5) Source(7, 1) + SourceIndex(0)
-2 >Emitted(19, 19) Source(7, 2) + SourceIndex(0)
+1->Emitted(23, 5) Source(7, 1) + SourceIndex(0)
+2 >Emitted(23, 19) Source(7, 2) + SourceIndex(0)
 ---
 >>>}(AbstractGreeter));
 1->
@@ -165,11 +169,11 @@ sourceFile:sourceMapValidationClassWithDefaultConstructorAndExtendsClause.ts
   >                     public a = 10;
   >                     public nameA = "Ten";
   >                 }
-1->Emitted(20, 1) Source(7, 1) + SourceIndex(0)
-2 >Emitted(20, 2) Source(7, 2) + SourceIndex(0)
-3 >Emitted(20, 2) Source(4, 1) + SourceIndex(0)
-4 >Emitted(20, 3) Source(4, 23) + SourceIndex(0)
-5 >Emitted(20, 18) Source(4, 38) + SourceIndex(0)
-6 >Emitted(20, 21) Source(7, 2) + SourceIndex(0)
+1->Emitted(24, 1) Source(7, 1) + SourceIndex(0)
+2 >Emitted(24, 2) Source(7, 2) + SourceIndex(0)
+3 >Emitted(24, 2) Source(4, 1) + SourceIndex(0)
+4 >Emitted(24, 3) Source(4, 23) + SourceIndex(0)
+5 >Emitted(24, 18) Source(4, 38) + SourceIndex(0)
+6 >Emitted(24, 21) Source(7, 2) + SourceIndex(0)
 ---
 >>>//# sourceMappingURL=sourceMapValidationClassWithDefaultConstructorAndExtendsClause.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/specializedInheritedConstructors1.js b/tests/baselines/reference/specializedInheritedConstructors1.js
index 56fd271bb34..2560437b43d 100644
--- a/tests/baselines/reference/specializedInheritedConstructors1.js
+++ b/tests/baselines/reference/specializedInheritedConstructors1.js
@@ -19,7 +19,11 @@ var myView = new MyView(m); // was error
 
 //// [specializedInheritedConstructors1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/specializedOverloadWithRestParameters.js b/tests/baselines/reference/specializedOverloadWithRestParameters.js
index 3f31e7f61df..0ea23b1b850 100644
--- a/tests/baselines/reference/specializedOverloadWithRestParameters.js
+++ b/tests/baselines/reference/specializedOverloadWithRestParameters.js
@@ -14,7 +14,11 @@ function g(tagName: any): Base {
 
 //// [specializedOverloadWithRestParameters.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/staticFactory1.js b/tests/baselines/reference/staticFactory1.js
index d8c53470b81..e9e4a286eb6 100644
--- a/tests/baselines/reference/staticFactory1.js
+++ b/tests/baselines/reference/staticFactory1.js
@@ -15,7 +15,11 @@ d.foo();
 
 //// [staticFactory1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/staticInheritance.js b/tests/baselines/reference/staticInheritance.js
index c6c95c1e6bf..181c8aa9659 100644
--- a/tests/baselines/reference/staticInheritance.js
+++ b/tests/baselines/reference/staticInheritance.js
@@ -13,7 +13,11 @@ doThing(B); //OK
 
 //// [staticInheritance.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/staticMemberAccessOffDerivedType1.js b/tests/baselines/reference/staticMemberAccessOffDerivedType1.js
index ededeec9c5c..6634d3c3519 100644
--- a/tests/baselines/reference/staticMemberAccessOffDerivedType1.js
+++ b/tests/baselines/reference/staticMemberAccessOffDerivedType1.js
@@ -11,7 +11,11 @@ class P extends SomeBase {
 
 //// [staticMemberAccessOffDerivedType1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/staticPropSuper.js b/tests/baselines/reference/staticPropSuper.js
index fdb63a556e0..10519dace00 100644
--- a/tests/baselines/reference/staticPropSuper.js
+++ b/tests/baselines/reference/staticPropSuper.js
@@ -37,7 +37,11 @@ class E extends A {
 
 //// [staticPropSuper.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/strictModeInConstructor.js b/tests/baselines/reference/strictModeInConstructor.js
index ac78decef58..0598932c4bb 100644
--- a/tests/baselines/reference/strictModeInConstructor.js
+++ b/tests/baselines/reference/strictModeInConstructor.js
@@ -62,7 +62,11 @@ class Ds extends A {
 
 //// [strictModeInConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/strictModeReservedWord.js b/tests/baselines/reference/strictModeReservedWord.js
index e376167c667..f15efc6e765 100644
--- a/tests/baselines/reference/strictModeReservedWord.js
+++ b/tests/baselines/reference/strictModeReservedWord.js
@@ -29,7 +29,11 @@ function foo() {
 
 //// [strictModeReservedWord.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/strictModeReservedWordInClassDeclaration.js b/tests/baselines/reference/strictModeReservedWordInClassDeclaration.js
index f6b864047a8..6f13aac7608 100644
--- a/tests/baselines/reference/strictModeReservedWordInClassDeclaration.js
+++ b/tests/baselines/reference/strictModeReservedWordInClassDeclaration.js
@@ -30,7 +30,11 @@ class H extends package.A { }
 
 //// [strictModeReservedWordInClassDeclaration.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/stringIndexerConstrainsPropertyDeclarations2.js b/tests/baselines/reference/stringIndexerConstrainsPropertyDeclarations2.js
index 6836a7adff3..adcc83a1841 100644
--- a/tests/baselines/reference/stringIndexerConstrainsPropertyDeclarations2.js
+++ b/tests/baselines/reference/stringIndexerConstrainsPropertyDeclarations2.js
@@ -42,7 +42,11 @@ var b: { [x: string]: A } = {
 //// [stringIndexerConstrainsPropertyDeclarations2.js]
 // String indexer providing a constraint of a user defined type
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypesOfTypeParameter.js b/tests/baselines/reference/subtypesOfTypeParameter.js
index 4407e02a1e7..2d42c1e4d79 100644
--- a/tests/baselines/reference/subtypesOfTypeParameter.js
+++ b/tests/baselines/reference/subtypesOfTypeParameter.js
@@ -108,7 +108,11 @@ function f2<T, U>(x: T, y: U) {
 //// [subtypesOfTypeParameter.js]
 // checking whether other types are subtypes of type parameters
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypesOfTypeParameterWithConstraints.js b/tests/baselines/reference/subtypesOfTypeParameterWithConstraints.js
index ec44364d4a4..a3b5ecaeb26 100644
--- a/tests/baselines/reference/subtypesOfTypeParameterWithConstraints.js
+++ b/tests/baselines/reference/subtypesOfTypeParameterWithConstraints.js
@@ -170,7 +170,11 @@ class D29<T extends U, U extends V, V extends Date> extends C3<V> {
 //// [subtypesOfTypeParameterWithConstraints.js]
 // checking whether other types are subtypes of type parameters with constraints
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypesOfTypeParameterWithConstraints4.js b/tests/baselines/reference/subtypesOfTypeParameterWithConstraints4.js
index f25a43a353f..1aa94ba7c99 100644
--- a/tests/baselines/reference/subtypesOfTypeParameterWithConstraints4.js
+++ b/tests/baselines/reference/subtypesOfTypeParameterWithConstraints4.js
@@ -81,7 +81,11 @@ class D9<T extends Foo, U extends Foo, V> extends B1<U> {
 //// [subtypesOfTypeParameterWithConstraints4.js]
 // checking whether other types are subtypes of type parameters with constraints
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypesOfTypeParameterWithRecursiveConstraints.js b/tests/baselines/reference/subtypesOfTypeParameterWithRecursiveConstraints.js
index 16797d0e5b5..05cc496f25a 100644
--- a/tests/baselines/reference/subtypesOfTypeParameterWithRecursiveConstraints.js
+++ b/tests/baselines/reference/subtypesOfTypeParameterWithRecursiveConstraints.js
@@ -160,7 +160,11 @@ module M2 {
 //// [subtypesOfTypeParameterWithRecursiveConstraints.js]
 // checking whether other types are subtypes of type parameters with constraints
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingTransitivity.js b/tests/baselines/reference/subtypingTransitivity.js
index ca52f7ed49f..5c06121d5a2 100644
--- a/tests/baselines/reference/subtypingTransitivity.js
+++ b/tests/baselines/reference/subtypingTransitivity.js
@@ -21,7 +21,11 @@ b.x = 1; // assigned number to string
 
 //// [subtypingTransitivity.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithCallSignatures2.js b/tests/baselines/reference/subtypingWithCallSignatures2.js
index 8086362951f..6b82e0d4841 100644
--- a/tests/baselines/reference/subtypingWithCallSignatures2.js
+++ b/tests/baselines/reference/subtypingWithCallSignatures2.js
@@ -175,7 +175,11 @@ var r18 = foo18(r18arg1);
 //// [subtypingWithCallSignatures2.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithCallSignatures3.js b/tests/baselines/reference/subtypingWithCallSignatures3.js
index 1fa01910cdb..49405cbd070 100644
--- a/tests/baselines/reference/subtypingWithCallSignatures3.js
+++ b/tests/baselines/reference/subtypingWithCallSignatures3.js
@@ -122,7 +122,11 @@ module WithGenericSignaturesInBaseType {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // error cases, so function calls will all result in 'any'
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithCallSignatures4.js b/tests/baselines/reference/subtypingWithCallSignatures4.js
index 5aaa139f19a..2e526d41fba 100644
--- a/tests/baselines/reference/subtypingWithCallSignatures4.js
+++ b/tests/baselines/reference/subtypingWithCallSignatures4.js
@@ -114,7 +114,11 @@ var r18 = foo18(r18arg);
 //// [subtypingWithCallSignatures4.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithConstructSignatures2.js b/tests/baselines/reference/subtypingWithConstructSignatures2.js
index 1f7ae528b5b..867beb93596 100644
--- a/tests/baselines/reference/subtypingWithConstructSignatures2.js
+++ b/tests/baselines/reference/subtypingWithConstructSignatures2.js
@@ -175,7 +175,11 @@ var r18 = foo18(r18arg1);
 //// [subtypingWithConstructSignatures2.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithConstructSignatures3.js b/tests/baselines/reference/subtypingWithConstructSignatures3.js
index d86b0519ebe..f13a56664ce 100644
--- a/tests/baselines/reference/subtypingWithConstructSignatures3.js
+++ b/tests/baselines/reference/subtypingWithConstructSignatures3.js
@@ -124,7 +124,11 @@ module WithGenericSignaturesInBaseType {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // error cases, so function calls will all result in 'any'
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithConstructSignatures4.js b/tests/baselines/reference/subtypingWithConstructSignatures4.js
index f11d2e3c211..32f9b33fc71 100644
--- a/tests/baselines/reference/subtypingWithConstructSignatures4.js
+++ b/tests/baselines/reference/subtypingWithConstructSignatures4.js
@@ -114,7 +114,11 @@ var r18 = foo18(r18arg);
 //// [subtypingWithConstructSignatures4.js]
 // checking subtype relations for function types as it relates to contextual signature instantiation
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithConstructSignatures5.js b/tests/baselines/reference/subtypingWithConstructSignatures5.js
index bdce522f104..2c177201732 100644
--- a/tests/baselines/reference/subtypingWithConstructSignatures5.js
+++ b/tests/baselines/reference/subtypingWithConstructSignatures5.js
@@ -52,7 +52,11 @@ interface I extends B {
 // checking subtype relations for function types as it relates to contextual signature instantiation
 // same as subtypingWithConstructSignatures2 just with an extra level of indirection in the inheritance chain
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithConstructSignatures6.js b/tests/baselines/reference/subtypingWithConstructSignatures6.js
index 2c0b10744f2..065d312c086 100644
--- a/tests/baselines/reference/subtypingWithConstructSignatures6.js
+++ b/tests/baselines/reference/subtypingWithConstructSignatures6.js
@@ -55,7 +55,11 @@ interface I9<T> extends A {
 // same as subtypingWithConstructSignatures4 but using class type parameters instead of generic signatures
 // all are errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithNumericIndexer.js b/tests/baselines/reference/subtypingWithNumericIndexer.js
index efe3d5927a9..1c1ade16a08 100644
--- a/tests/baselines/reference/subtypingWithNumericIndexer.js
+++ b/tests/baselines/reference/subtypingWithNumericIndexer.js
@@ -42,7 +42,11 @@ module Generics {
 //// [subtypingWithNumericIndexer.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithNumericIndexer3.js b/tests/baselines/reference/subtypingWithNumericIndexer3.js
index a3b1034d6a8..2c0da66f8c9 100644
--- a/tests/baselines/reference/subtypingWithNumericIndexer3.js
+++ b/tests/baselines/reference/subtypingWithNumericIndexer3.js
@@ -46,7 +46,11 @@ module Generics {
 //// [subtypingWithNumericIndexer3.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithNumericIndexer4.js b/tests/baselines/reference/subtypingWithNumericIndexer4.js
index f2657654c8b..1881825eb24 100644
--- a/tests/baselines/reference/subtypingWithNumericIndexer4.js
+++ b/tests/baselines/reference/subtypingWithNumericIndexer4.js
@@ -30,7 +30,11 @@ module Generics {
 //// [subtypingWithNumericIndexer4.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithObjectMembers.js b/tests/baselines/reference/subtypingWithObjectMembers.js
index 04f05b81cef..263bb117d34 100644
--- a/tests/baselines/reference/subtypingWithObjectMembers.js
+++ b/tests/baselines/reference/subtypingWithObjectMembers.js
@@ -69,7 +69,11 @@ module TwoLevels {
 
 //// [subtypingWithObjectMembers.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithObjectMembers4.js b/tests/baselines/reference/subtypingWithObjectMembers4.js
index 2cdf1b4401b..03d7228b2f9 100644
--- a/tests/baselines/reference/subtypingWithObjectMembers4.js
+++ b/tests/baselines/reference/subtypingWithObjectMembers4.js
@@ -36,7 +36,11 @@ class B3 extends A3 {
 //// [subtypingWithObjectMembers4.js]
 // subtyping when property names do not match
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithObjectMembersAccessibility.js b/tests/baselines/reference/subtypingWithObjectMembersAccessibility.js
index 386ce781675..0eb506d3210 100644
--- a/tests/baselines/reference/subtypingWithObjectMembersAccessibility.js
+++ b/tests/baselines/reference/subtypingWithObjectMembersAccessibility.js
@@ -36,7 +36,11 @@ class B3 extends A3 {
 //// [subtypingWithObjectMembersAccessibility.js]
 // Derived member is private, base member is not causes errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithObjectMembersAccessibility2.js b/tests/baselines/reference/subtypingWithObjectMembersAccessibility2.js
index 5227eac7db4..f171736911b 100644
--- a/tests/baselines/reference/subtypingWithObjectMembersAccessibility2.js
+++ b/tests/baselines/reference/subtypingWithObjectMembersAccessibility2.js
@@ -64,7 +64,11 @@ module ImplicitPublic {
 //// [subtypingWithObjectMembersAccessibility2.js]
 // Derived member is private, base member is not causes errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithStringIndexer.js b/tests/baselines/reference/subtypingWithStringIndexer.js
index a1ec5e1f46f..bffca920982 100644
--- a/tests/baselines/reference/subtypingWithStringIndexer.js
+++ b/tests/baselines/reference/subtypingWithStringIndexer.js
@@ -43,7 +43,11 @@ module Generics {
 //// [subtypingWithStringIndexer.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithStringIndexer3.js b/tests/baselines/reference/subtypingWithStringIndexer3.js
index ea193a206ed..0ff4b73c848 100644
--- a/tests/baselines/reference/subtypingWithStringIndexer3.js
+++ b/tests/baselines/reference/subtypingWithStringIndexer3.js
@@ -46,7 +46,11 @@ module Generics {
 //// [subtypingWithStringIndexer3.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/subtypingWithStringIndexer4.js b/tests/baselines/reference/subtypingWithStringIndexer4.js
index b5a8c75a03e..347df7c1720 100644
--- a/tests/baselines/reference/subtypingWithStringIndexer4.js
+++ b/tests/baselines/reference/subtypingWithStringIndexer4.js
@@ -30,7 +30,11 @@ module Generics {
 //// [subtypingWithStringIndexer4.js]
 // Derived type indexer must be subtype of base type indexer
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/super.js b/tests/baselines/reference/super.js
index 6607c7897dd..bbf1862bd0f 100644
--- a/tests/baselines/reference/super.js
+++ b/tests/baselines/reference/super.js
@@ -39,7 +39,11 @@ s.foo() + ss.foo();
 
 //// [super.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/super1.js b/tests/baselines/reference/super1.js
index 44a48adab77..d437c923fe6 100644
--- a/tests/baselines/reference/super1.js
+++ b/tests/baselines/reference/super1.js
@@ -68,7 +68,11 @@ module Base4 {
 
 //// [super1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/super2.js b/tests/baselines/reference/super2.js
index e46b2825481..b8a679c4c8d 100644
--- a/tests/baselines/reference/super2.js
+++ b/tests/baselines/reference/super2.js
@@ -52,7 +52,11 @@ results1.x() + results1.y() + results2.y();
 
 //// [super2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superAccess.js b/tests/baselines/reference/superAccess.js
index b300f75b5fa..f2f6ccbaf4a 100644
--- a/tests/baselines/reference/superAccess.js
+++ b/tests/baselines/reference/superAccess.js
@@ -15,7 +15,11 @@ class MyDerived extends MyBase {
 
 //// [superAccess.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superAccess2.js b/tests/baselines/reference/superAccess2.js
index 0388b8d7f10..021589c1e79 100644
--- a/tests/baselines/reference/superAccess2.js
+++ b/tests/baselines/reference/superAccess2.js
@@ -26,7 +26,11 @@ class Q extends P {
 
 //// [superAccess2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superAccessInFatArrow1.js b/tests/baselines/reference/superAccessInFatArrow1.js
index ec8488f0dad..e62db8c823b 100644
--- a/tests/baselines/reference/superAccessInFatArrow1.js
+++ b/tests/baselines/reference/superAccessInFatArrow1.js
@@ -17,7 +17,11 @@ module test {
 
 //// [superAccessInFatArrow1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallArgsMustMatch.js b/tests/baselines/reference/superCallArgsMustMatch.js
index 7ca13891555..ec83550a9f0 100644
--- a/tests/baselines/reference/superCallArgsMustMatch.js
+++ b/tests/baselines/reference/superCallArgsMustMatch.js
@@ -27,7 +27,11 @@ class T6 extends T5<number>{
 
 //// [superCallArgsMustMatch.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallAssignResult.js b/tests/baselines/reference/superCallAssignResult.js
index d7ad39fc7a6..f1407cac107 100644
--- a/tests/baselines/reference/superCallAssignResult.js
+++ b/tests/baselines/reference/superCallAssignResult.js
@@ -12,7 +12,11 @@ class H extends E {
 
 //// [superCallAssignResult.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing1.js b/tests/baselines/reference/superCallBeforeThisAccessing1.js
index 916d1568232..151e9da2f15 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing1.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing1.js
@@ -18,7 +18,11 @@ class D extends Base {
 
 //// [superCallBeforeThisAccessing1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing2.js b/tests/baselines/reference/superCallBeforeThisAccessing2.js
index c5a8d293fff..7655b2df83b 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing2.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing2.js
@@ -12,7 +12,11 @@ class D extends Base {
 
 //// [superCallBeforeThisAccessing2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing3.js b/tests/baselines/reference/superCallBeforeThisAccessing3.js
index 8a59226d1d6..34555c677ba 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing3.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing3.js
@@ -15,7 +15,11 @@ class D extends Base {
 
 //// [superCallBeforeThisAccessing3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing4.js b/tests/baselines/reference/superCallBeforeThisAccessing4.js
index 6870662435e..9fc2987e96e 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing4.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing4.js
@@ -17,7 +17,11 @@ class E extends null {
 
 //// [superCallBeforeThisAccessing4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing5.js b/tests/baselines/reference/superCallBeforeThisAccessing5.js
index 0c2f3aa1c2d..1f3b0040e49 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing5.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing5.js
@@ -9,7 +9,11 @@ class D extends null {
 
 //// [superCallBeforeThisAccessing5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing6.js b/tests/baselines/reference/superCallBeforeThisAccessing6.js
index 2fe03ab52b5..740f90d2e2b 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing6.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing6.js
@@ -12,7 +12,11 @@ class D extends Base {
 
 //// [superCallBeforeThisAccessing6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing7.js b/tests/baselines/reference/superCallBeforeThisAccessing7.js
index a843456be76..65d95769c40 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing7.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing7.js
@@ -15,7 +15,11 @@ class D extends Base {
 
 //// [superCallBeforeThisAccessing7.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallBeforeThisAccessing8.js b/tests/baselines/reference/superCallBeforeThisAccessing8.js
index 3b23949584f..b5e454139c0 100644
--- a/tests/baselines/reference/superCallBeforeThisAccessing8.js
+++ b/tests/baselines/reference/superCallBeforeThisAccessing8.js
@@ -15,7 +15,11 @@ class D extends Base {
 
 //// [superCallBeforeThisAccessing8.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType1.js b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType1.js
index e4f1d4ed105..464c879212e 100644
--- a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType1.js
+++ b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType1.js
@@ -13,7 +13,11 @@ class D extends B<any> {
 
 //// [superCallFromClassThatDerivesFromGenericType1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType2.js b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType2.js
index 47d1b5007fe..6ebe47532c8 100644
--- a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType2.js
+++ b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericType2.js
@@ -12,7 +12,11 @@ class D extends B<any> {
 
 //// [superCallFromClassThatDerivesFromGenericType2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithIncorrectNumberOfTypeArguments1.js b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithIncorrectNumberOfTypeArguments1.js
index d29377ed246..19e480378a4 100644
--- a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithIncorrectNumberOfTypeArguments1.js
+++ b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithIncorrectNumberOfTypeArguments1.js
@@ -12,7 +12,11 @@ class B extends A<number> {
 
 //// [superCallFromClassThatDerivesFromGenericTypeButWithIncorrectNumberOfTypeArguments1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithNoTypeArguments1.js b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithNoTypeArguments1.js
index 844b24a0698..48855cb0d11 100644
--- a/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithNoTypeArguments1.js
+++ b/tests/baselines/reference/superCallFromClassThatDerivesFromGenericTypeButWithNoTypeArguments1.js
@@ -12,7 +12,11 @@ class B extends A {
 
 //// [superCallFromClassThatDerivesFromGenericTypeButWithNoTypeArguments1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallFromClassThatDerivesNonGenericTypeButWithTypeArguments1.js b/tests/baselines/reference/superCallFromClassThatDerivesNonGenericTypeButWithTypeArguments1.js
index 71587371fa0..abfe5294a93 100644
--- a/tests/baselines/reference/superCallFromClassThatDerivesNonGenericTypeButWithTypeArguments1.js
+++ b/tests/baselines/reference/superCallFromClassThatDerivesNonGenericTypeButWithTypeArguments1.js
@@ -12,7 +12,11 @@ class B extends A<number, string> {
 
 //// [superCallFromClassThatDerivesNonGenericTypeButWithTypeArguments1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallInNonStaticMethod.js b/tests/baselines/reference/superCallInNonStaticMethod.js
index 99a026a38fd..dbea09ebced 100644
--- a/tests/baselines/reference/superCallInNonStaticMethod.js
+++ b/tests/baselines/reference/superCallInNonStaticMethod.js
@@ -52,7 +52,11 @@ class Other extends Doing {
 
 //// [superCallInNonStaticMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallInStaticMethod.js b/tests/baselines/reference/superCallInStaticMethod.js
index b65b2b270c5..104f8821dca 100644
--- a/tests/baselines/reference/superCallInStaticMethod.js
+++ b/tests/baselines/reference/superCallInStaticMethod.js
@@ -48,7 +48,11 @@ class Other extends Doing {
 
 //// [superCallInStaticMethod.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallInsideClassDeclaration.js b/tests/baselines/reference/superCallInsideClassDeclaration.js
index 0b6c768c86f..4f7a0087ab1 100644
--- a/tests/baselines/reference/superCallInsideClassDeclaration.js
+++ b/tests/baselines/reference/superCallInsideClassDeclaration.js
@@ -18,7 +18,11 @@ class B extends A {
 
 //// [superCallInsideClassDeclaration.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallInsideClassExpression.js b/tests/baselines/reference/superCallInsideClassExpression.js
index c3bd2425dd4..01bce40d204 100644
--- a/tests/baselines/reference/superCallInsideClassExpression.js
+++ b/tests/baselines/reference/superCallInsideClassExpression.js
@@ -18,7 +18,11 @@ class B extends A {
 
 //// [superCallInsideClassExpression.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallInsideObjectLiteralExpression.js b/tests/baselines/reference/superCallInsideObjectLiteralExpression.js
index 45b6301a871..613997e789f 100644
--- a/tests/baselines/reference/superCallInsideObjectLiteralExpression.js
+++ b/tests/baselines/reference/superCallInsideObjectLiteralExpression.js
@@ -14,7 +14,11 @@ class B extends A {
 
 //// [superCallInsideObjectLiteralExpression.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallOutsideConstructor.js b/tests/baselines/reference/superCallOutsideConstructor.js
index a98a9b3a322..0e1f3fbd837 100644
--- a/tests/baselines/reference/superCallOutsideConstructor.js
+++ b/tests/baselines/reference/superCallOutsideConstructor.js
@@ -24,7 +24,11 @@ var d = new D();
 
 //// [superCallOutsideConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallParameterContextualTyping1.js b/tests/baselines/reference/superCallParameterContextualTyping1.js
index 46aeb976987..132cb003921 100644
--- a/tests/baselines/reference/superCallParameterContextualTyping1.js
+++ b/tests/baselines/reference/superCallParameterContextualTyping1.js
@@ -14,7 +14,11 @@ class B extends A<number, string> {
 
 //// [superCallParameterContextualTyping1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallParameterContextualTyping2.js b/tests/baselines/reference/superCallParameterContextualTyping2.js
index a6aed2d1cae..bbb0871d385 100644
--- a/tests/baselines/reference/superCallParameterContextualTyping2.js
+++ b/tests/baselines/reference/superCallParameterContextualTyping2.js
@@ -13,7 +13,11 @@ class C extends A<number, string> {
 
 //// [superCallParameterContextualTyping2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallParameterContextualTyping3.js b/tests/baselines/reference/superCallParameterContextualTyping3.js
index 8445e86cfce..4469c918b31 100644
--- a/tests/baselines/reference/superCallParameterContextualTyping3.js
+++ b/tests/baselines/reference/superCallParameterContextualTyping3.js
@@ -33,7 +33,11 @@ class C extends CBase<string> {
 
 //// [superCallParameterContextualTyping3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallWithCommentEmit01.js b/tests/baselines/reference/superCallWithCommentEmit01.js
index ea23eb3be03..ae7f053e5d4 100644
--- a/tests/baselines/reference/superCallWithCommentEmit01.js
+++ b/tests/baselines/reference/superCallWithCommentEmit01.js
@@ -12,7 +12,11 @@ class B extends A {
 
 //// [superCallWithCommentEmit01.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallWithMissingBaseClass.js b/tests/baselines/reference/superCallWithMissingBaseClass.js
index 9dff2bc4c56..766c121d42b 100644
--- a/tests/baselines/reference/superCallWithMissingBaseClass.js
+++ b/tests/baselines/reference/superCallWithMissingBaseClass.js
@@ -11,7 +11,11 @@ class Foo extends Bar {
 
 //// [superCallWithMissingBaseClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCalls.js b/tests/baselines/reference/superCalls.js
index d5a9af8e06a..47292405faf 100644
--- a/tests/baselines/reference/superCalls.js
+++ b/tests/baselines/reference/superCalls.js
@@ -32,7 +32,11 @@ class OtherDerived extends OtherBase {
 
 //// [superCalls.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superCallsInConstructor.js b/tests/baselines/reference/superCallsInConstructor.js
index 540eef99840..707757b37b6 100644
--- a/tests/baselines/reference/superCallsInConstructor.js
+++ b/tests/baselines/reference/superCallsInConstructor.js
@@ -22,7 +22,11 @@ class Derived extends Base {
 
 //// [superCallsInConstructor.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superErrors.js b/tests/baselines/reference/superErrors.js
index c52b2a22173..9b9681b2dee 100644
--- a/tests/baselines/reference/superErrors.js
+++ b/tests/baselines/reference/superErrors.js
@@ -53,7 +53,11 @@ class RegisteredUser extends User {
 
 //// [superErrors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superInCatchBlock1.js b/tests/baselines/reference/superInCatchBlock1.js
index 17ac62b8491..bf8f9bd5e02 100644
--- a/tests/baselines/reference/superInCatchBlock1.js
+++ b/tests/baselines/reference/superInCatchBlock1.js
@@ -15,7 +15,11 @@ class B extends A {
 
 //// [superInCatchBlock1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superInConstructorParam1.js b/tests/baselines/reference/superInConstructorParam1.js
index 7f53128e99e..869dfde8e51 100644
--- a/tests/baselines/reference/superInConstructorParam1.js
+++ b/tests/baselines/reference/superInConstructorParam1.js
@@ -12,7 +12,11 @@ class C extends B {
 
 //// [superInConstructorParam1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superInLambdas.js b/tests/baselines/reference/superInLambdas.js
index 8c3d37efb34..1e040f627c8 100644
--- a/tests/baselines/reference/superInLambdas.js
+++ b/tests/baselines/reference/superInLambdas.js
@@ -69,7 +69,11 @@ class RegisteredUser4 extends User {
 
 //// [superInLambdas.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superInObjectLiterals_ES5.js b/tests/baselines/reference/superInObjectLiterals_ES5.js
index f31a2492f3d..77f55772b69 100644
--- a/tests/baselines/reference/superInObjectLiterals_ES5.js
+++ b/tests/baselines/reference/superInObjectLiterals_ES5.js
@@ -61,7 +61,11 @@ class B extends A {
 
 //// [superInObjectLiterals_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superNewCall1.js b/tests/baselines/reference/superNewCall1.js
index 2b6231691b2..c532b4556c8 100644
--- a/tests/baselines/reference/superNewCall1.js
+++ b/tests/baselines/reference/superNewCall1.js
@@ -14,7 +14,11 @@ class B extends A<number, string> {
 
 //// [superNewCall1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superPropertyAccess.js b/tests/baselines/reference/superPropertyAccess.js
index 72353c27624..eb92e66a131 100644
--- a/tests/baselines/reference/superPropertyAccess.js
+++ b/tests/baselines/reference/superPropertyAccess.js
@@ -38,7 +38,11 @@ class MyDerived extends MyBase {
 
 //// [superPropertyAccess.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superPropertyAccess1.js b/tests/baselines/reference/superPropertyAccess1.js
index 7e07c236eec..f15bdde29e2 100644
--- a/tests/baselines/reference/superPropertyAccess1.js
+++ b/tests/baselines/reference/superPropertyAccess1.js
@@ -29,7 +29,11 @@ class D extends C {
 
 //// [superPropertyAccess1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superPropertyAccess2.js b/tests/baselines/reference/superPropertyAccess2.js
index f0776992312..98f1d0a190c 100644
--- a/tests/baselines/reference/superPropertyAccess2.js
+++ b/tests/baselines/reference/superPropertyAccess2.js
@@ -29,7 +29,11 @@ class D extends C {
 
 //// [superPropertyAccess2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superPropertyAccessInComputedPropertiesOfNestedType_ES5.js b/tests/baselines/reference/superPropertyAccessInComputedPropertiesOfNestedType_ES5.js
index cb5e98ee2d2..d60310be5e7 100644
--- a/tests/baselines/reference/superPropertyAccessInComputedPropertiesOfNestedType_ES5.js
+++ b/tests/baselines/reference/superPropertyAccessInComputedPropertiesOfNestedType_ES5.js
@@ -16,7 +16,11 @@ class B extends A {
 
 //// [superPropertyAccessInComputedPropertiesOfNestedType_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superPropertyAccessNoError.js b/tests/baselines/reference/superPropertyAccessNoError.js
index 0f4efbc719f..d2829eba561 100644
--- a/tests/baselines/reference/superPropertyAccessNoError.js
+++ b/tests/baselines/reference/superPropertyAccessNoError.js
@@ -78,7 +78,11 @@ instance.returnThis().fn();
 //super.publicStaticMemberFunction in static member function of derived class
 //super.publicStaticMemberFunction in static member accessor(get and set) of derived class
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superPropertyAccess_ES5.js b/tests/baselines/reference/superPropertyAccess_ES5.js
index 159b3b86c4c..e8f4dd3f872 100644
--- a/tests/baselines/reference/superPropertyAccess_ES5.js
+++ b/tests/baselines/reference/superPropertyAccess_ES5.js
@@ -31,7 +31,11 @@ class B extends A {
 
 //// [superPropertyAccess_ES5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superSymbolIndexedAccess5.js b/tests/baselines/reference/superSymbolIndexedAccess5.js
index 43565251f79..3c5aaf9b843 100644
--- a/tests/baselines/reference/superSymbolIndexedAccess5.js
+++ b/tests/baselines/reference/superSymbolIndexedAccess5.js
@@ -15,7 +15,11 @@ class Bar extends Foo {
 
 //// [superSymbolIndexedAccess5.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superSymbolIndexedAccess6.js b/tests/baselines/reference/superSymbolIndexedAccess6.js
index 2f47d38660e..ff11a4c1b65 100644
--- a/tests/baselines/reference/superSymbolIndexedAccess6.js
+++ b/tests/baselines/reference/superSymbolIndexedAccess6.js
@@ -15,7 +15,11 @@ class Bar extends Foo {
 
 //// [superSymbolIndexedAccess6.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superWithGenericSpecialization.js b/tests/baselines/reference/superWithGenericSpecialization.js
index e024285dc9e..8e23bfb25c4 100644
--- a/tests/baselines/reference/superWithGenericSpecialization.js
+++ b/tests/baselines/reference/superWithGenericSpecialization.js
@@ -16,7 +16,11 @@ var r2: number = d.y;
 
 //// [superWithGenericSpecialization.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superWithGenerics.js b/tests/baselines/reference/superWithGenerics.js
index c8c99ef56cf..5e83df296d2 100644
--- a/tests/baselines/reference/superWithGenerics.js
+++ b/tests/baselines/reference/superWithGenerics.js
@@ -13,7 +13,11 @@ class D extends B<any> {
 
 //// [superWithGenerics.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superWithTypeArgument.js b/tests/baselines/reference/superWithTypeArgument.js
index 638b970d7ff..51a4f93a4e4 100644
--- a/tests/baselines/reference/superWithTypeArgument.js
+++ b/tests/baselines/reference/superWithTypeArgument.js
@@ -11,7 +11,11 @@ class D<T> extends C {
 
 //// [superWithTypeArgument.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superWithTypeArgument2.js b/tests/baselines/reference/superWithTypeArgument2.js
index 4241cc6a699..3744e797615 100644
--- a/tests/baselines/reference/superWithTypeArgument2.js
+++ b/tests/baselines/reference/superWithTypeArgument2.js
@@ -11,7 +11,11 @@ class D<T> extends C<T> {
 
 //// [superWithTypeArgument2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/superWithTypeArgument3.js b/tests/baselines/reference/superWithTypeArgument3.js
index 8f9d6252a87..9f76cc1ecff 100644
--- a/tests/baselines/reference/superWithTypeArgument3.js
+++ b/tests/baselines/reference/superWithTypeArgument3.js
@@ -15,7 +15,11 @@ class D<T> extends C<T> {
 
 //// [superWithTypeArgument3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/super_inside-object-literal-getters-and-setters.js b/tests/baselines/reference/super_inside-object-literal-getters-and-setters.js
index e244f318328..077affd0eda 100644
--- a/tests/baselines/reference/super_inside-object-literal-getters-and-setters.js
+++ b/tests/baselines/reference/super_inside-object-literal-getters-and-setters.js
@@ -29,7 +29,11 @@ class SuperObjectTest extends F {
 
 //// [super_inside-object-literal-getters-and-setters.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/switchStatements.js b/tests/baselines/reference/switchStatements.js
index 20a92712670..05a7fafb046 100644
--- a/tests/baselines/reference/switchStatements.js
+++ b/tests/baselines/reference/switchStatements.js
@@ -57,7 +57,11 @@ switch ((<T>(x: T) => '')(1)) { }
 
 //// [switchStatements.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/systemModuleWithSuperClass.js b/tests/baselines/reference/systemModuleWithSuperClass.js
index cbb2b5d05dd..e31370d0acd 100644
--- a/tests/baselines/reference/systemModuleWithSuperClass.js
+++ b/tests/baselines/reference/systemModuleWithSuperClass.js
@@ -33,7 +33,11 @@ System.register([], function (exports_1, context_1) {
 System.register(["./foo"], function (exports_1, context_1) {
     "use strict";
     var __extends = (this && this.__extends) || function (d, b) {
-        Object.setPrototypeOf(d, b);
+        if (typeof Object.setPrototypeOf === "function") {
+            Object.setPrototypeOf(d, b);
+        } else {
+            d.__proto__ = b;
+        }
         function __() { this.constructor = d; }
         d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
     };
diff --git a/tests/baselines/reference/targetTypeBaseCalls.js b/tests/baselines/reference/targetTypeBaseCalls.js
index 3c1daae5d31..d359aa91628 100644
--- a/tests/baselines/reference/targetTypeBaseCalls.js
+++ b/tests/baselines/reference/targetTypeBaseCalls.js
@@ -20,7 +20,11 @@ class Bar extends Foo { constructor() { super(function(s) { s = 5 }) } }  // err
 
 //// [targetTypeBaseCalls.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisInInvalidContexts.js b/tests/baselines/reference/thisInInvalidContexts.js
index 5eaac48383c..6b16742cca2 100644
--- a/tests/baselines/reference/thisInInvalidContexts.js
+++ b/tests/baselines/reference/thisInInvalidContexts.js
@@ -50,7 +50,11 @@ enum SomeEnum {
 
 //// [thisInInvalidContexts.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisInInvalidContextsExternalModule.js b/tests/baselines/reference/thisInInvalidContextsExternalModule.js
index 788eb974e89..68579bb2368 100644
--- a/tests/baselines/reference/thisInInvalidContextsExternalModule.js
+++ b/tests/baselines/reference/thisInInvalidContextsExternalModule.js
@@ -51,7 +51,11 @@ export = this; // Should be an error
 //// [thisInInvalidContextsExternalModule.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisInSuperCall.js b/tests/baselines/reference/thisInSuperCall.js
index f49a0b8eb65..b8120fe732c 100644
--- a/tests/baselines/reference/thisInSuperCall.js
+++ b/tests/baselines/reference/thisInSuperCall.js
@@ -24,7 +24,11 @@ class Foo3 extends Base {
 
 //// [thisInSuperCall.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisInSuperCall1.js b/tests/baselines/reference/thisInSuperCall1.js
index bfc9d8b4f17..3adc1c2a5b3 100644
--- a/tests/baselines/reference/thisInSuperCall1.js
+++ b/tests/baselines/reference/thisInSuperCall1.js
@@ -12,7 +12,11 @@ class Foo extends Base {
 
 //// [thisInSuperCall1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisInSuperCall2.js b/tests/baselines/reference/thisInSuperCall2.js
index df5dee1a321..f310654acae 100644
--- a/tests/baselines/reference/thisInSuperCall2.js
+++ b/tests/baselines/reference/thisInSuperCall2.js
@@ -21,7 +21,11 @@ class Foo2 extends Base {
 
 //// [thisInSuperCall2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisInSuperCall3.js b/tests/baselines/reference/thisInSuperCall3.js
index ac47e685c38..b0f4d62c746 100644
--- a/tests/baselines/reference/thisInSuperCall3.js
+++ b/tests/baselines/reference/thisInSuperCall3.js
@@ -14,7 +14,11 @@ class Foo extends Base {
 
 //// [thisInSuperCall3.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisTypeInFunctions.js b/tests/baselines/reference/thisTypeInFunctions.js
index 3169e0cd06b..ae95aac22b5 100644
--- a/tests/baselines/reference/thisTypeInFunctions.js
+++ b/tests/baselines/reference/thisTypeInFunctions.js
@@ -196,7 +196,11 @@ function missingTypeIsImplicitAny(this, a: number) { return this.anything + a; }
 
 //// [thisTypeInFunctions.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/thisTypeInFunctionsNegative.js b/tests/baselines/reference/thisTypeInFunctionsNegative.js
index 4b936e0198f..2591f9fe019 100644
--- a/tests/baselines/reference/thisTypeInFunctionsNegative.js
+++ b/tests/baselines/reference/thisTypeInFunctionsNegative.js
@@ -178,7 +178,11 @@ c.explicitProperty = (this, m) => m + this.n;
 
 //// [thisTypeInFunctionsNegative.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxCorrectlyParseLessThanComparison1.js b/tests/baselines/reference/tsxCorrectlyParseLessThanComparison1.js
index 6cfb957dd39..b6c5295b482 100644
--- a/tests/baselines/reference/tsxCorrectlyParseLessThanComparison1.js
+++ b/tests/baselines/reference/tsxCorrectlyParseLessThanComparison1.js
@@ -22,7 +22,11 @@ export class ShortDetails extends React.Component<{ id: number }, {}> {
 //// [tsxCorrectlyParseLessThanComparison1.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxDynamicTagName5.js b/tests/baselines/reference/tsxDynamicTagName5.js
index 200a8e2d78d..3a1ac6d2246 100644
--- a/tests/baselines/reference/tsxDynamicTagName5.js
+++ b/tests/baselines/reference/tsxDynamicTagName5.js
@@ -22,7 +22,11 @@ export class Text extends React.Component<{}, {}> {
 //// [app.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxDynamicTagName7.js b/tests/baselines/reference/tsxDynamicTagName7.js
index 717caa83310..f584dbf960a 100644
--- a/tests/baselines/reference/tsxDynamicTagName7.js
+++ b/tests/baselines/reference/tsxDynamicTagName7.js
@@ -22,7 +22,11 @@ export class Text extends React.Component<{}, {}> {
 //// [app.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxDynamicTagName8.js b/tests/baselines/reference/tsxDynamicTagName8.js
index 725eeec0326..bf3ab5d4a69 100644
--- a/tests/baselines/reference/tsxDynamicTagName8.js
+++ b/tests/baselines/reference/tsxDynamicTagName8.js
@@ -22,7 +22,11 @@ export class Text extends React.Component<{}, {}> {
 //// [app.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxDynamicTagName9.js b/tests/baselines/reference/tsxDynamicTagName9.js
index ff7e4a9a7e2..fefa118d704 100644
--- a/tests/baselines/reference/tsxDynamicTagName9.js
+++ b/tests/baselines/reference/tsxDynamicTagName9.js
@@ -22,7 +22,11 @@ export class Text extends React.Component<{}, {}> {
 //// [app.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxExternalModuleEmit1.js b/tests/baselines/reference/tsxExternalModuleEmit1.js
index 0d515ac2114..29f4e78100e 100644
--- a/tests/baselines/reference/tsxExternalModuleEmit1.js
+++ b/tests/baselines/reference/tsxExternalModuleEmit1.js
@@ -34,7 +34,11 @@ export class Button extends React.Component<any, any> {
 //// [button.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
@@ -53,7 +57,11 @@ exports.Button = Button;
 //// [app.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxStatelessFunctionComponents2.js b/tests/baselines/reference/tsxStatelessFunctionComponents2.js
index 7352f7edef7..75284a28702 100644
--- a/tests/baselines/reference/tsxStatelessFunctionComponents2.js
+++ b/tests/baselines/reference/tsxStatelessFunctionComponents2.js
@@ -41,7 +41,11 @@ let i = <div ref={x => x.propertyNotOnHtmlDivElement} />;
 //// [file.jsx]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/tsxUnionTypeComponent1.js b/tests/baselines/reference/tsxUnionTypeComponent1.js
index a832e26806e..215046ba2b6 100644
--- a/tests/baselines/reference/tsxUnionTypeComponent1.js
+++ b/tests/baselines/reference/tsxUnionTypeComponent1.js
@@ -27,7 +27,11 @@ class MyButtonComponent extends React.Component<{},{}> {
 //// [file.js]
 "use strict";
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeAssertions.js b/tests/baselines/reference/typeAssertions.js
index 9e7e39be710..e3cf89b0800 100644
--- a/tests/baselines/reference/typeAssertions.js
+++ b/tests/baselines/reference/typeAssertions.js
@@ -53,7 +53,11 @@ if((numOrStr === undefined) as numOrStr is string) { // Error
 
 //// [typeAssertions.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardFunction.js b/tests/baselines/reference/typeGuardFunction.js
index e261492d35f..f16b6d1ce5a 100644
--- a/tests/baselines/reference/typeGuardFunction.js
+++ b/tests/baselines/reference/typeGuardFunction.js
@@ -85,7 +85,11 @@ let union3: boolean | B = isA(union2) || union2;
 
 //// [typeGuardFunction.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardFunctionErrors.js b/tests/baselines/reference/typeGuardFunctionErrors.js
index 2ceec7e12e2..3e9b8f08cd4 100644
--- a/tests/baselines/reference/typeGuardFunctionErrors.js
+++ b/tests/baselines/reference/typeGuardFunctionErrors.js
@@ -147,7 +147,11 @@ if (hasMissingParameter()) {
 
 //// [typeGuardFunctionErrors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardFunctionGenerics.js b/tests/baselines/reference/typeGuardFunctionGenerics.js
index a2b9df419ad..ffe263f9985 100644
--- a/tests/baselines/reference/typeGuardFunctionGenerics.js
+++ b/tests/baselines/reference/typeGuardFunctionGenerics.js
@@ -35,7 +35,11 @@ let test3: B = funE(isB, 1);
 
 //// [typeGuardFunctionGenerics.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardFunctionOfFormThis.js b/tests/baselines/reference/typeGuardFunctionOfFormThis.js
index f9f102e06ae..a1d1b7842d4 100644
--- a/tests/baselines/reference/typeGuardFunctionOfFormThis.js
+++ b/tests/baselines/reference/typeGuardFunctionOfFormThis.js
@@ -143,7 +143,11 @@ interface MimicGuardInterface {
 
 //// [typeGuardFunctionOfFormThis.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardFunctionOfFormThisErrors.js b/tests/baselines/reference/typeGuardFunctionOfFormThisErrors.js
index c1e5b6b0af1..7ec705bdc2d 100644
--- a/tests/baselines/reference/typeGuardFunctionOfFormThisErrors.js
+++ b/tests/baselines/reference/typeGuardFunctionOfFormThisErrors.js
@@ -61,7 +61,11 @@ else {
 
 //// [typeGuardFunctionOfFormThisErrors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardOfFormInstanceOf.js b/tests/baselines/reference/typeGuardOfFormInstanceOf.js
index 75f0ccdf492..67d216d0f58 100644
--- a/tests/baselines/reference/typeGuardOfFormInstanceOf.js
+++ b/tests/baselines/reference/typeGuardOfFormInstanceOf.js
@@ -74,7 +74,11 @@ else {
 //    it is a subtype of the type of x, or
 //  - when false, has no effect on the type of x.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardOfFormIsType.js b/tests/baselines/reference/typeGuardOfFormIsType.js
index c48034dfc36..88d0ac11a09 100644
--- a/tests/baselines/reference/typeGuardOfFormIsType.js
+++ b/tests/baselines/reference/typeGuardOfFormIsType.js
@@ -39,7 +39,11 @@ var r2: C2 | D1 = isC1(c2Ord1) && c2Ord1; // C2 | D1
 
 //// [typeGuardOfFormIsType.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardOfFormThisMember.js b/tests/baselines/reference/typeGuardOfFormThisMember.js
index eaaa656a08e..6dc97fb0152 100644
--- a/tests/baselines/reference/typeGuardOfFormThisMember.js
+++ b/tests/baselines/reference/typeGuardOfFormThisMember.js
@@ -84,7 +84,11 @@ namespace Test {
 
 //// [typeGuardOfFormThisMember.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeGuardOfFormThisMemberErrors.js b/tests/baselines/reference/typeGuardOfFormThisMemberErrors.js
index cb7fa087fe1..fbc2f23e547 100644
--- a/tests/baselines/reference/typeGuardOfFormThisMemberErrors.js
+++ b/tests/baselines/reference/typeGuardOfFormThisMemberErrors.js
@@ -34,7 +34,11 @@ namespace Test {
 
 //// [typeGuardOfFormThisMemberErrors.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeMatch2.js b/tests/baselines/reference/typeMatch2.js
index 9721d17aac4..e4c7925a90b 100644
--- a/tests/baselines/reference/typeMatch2.js
+++ b/tests/baselines/reference/typeMatch2.js
@@ -46,7 +46,11 @@ function f4() {
 
 //// [typeMatch2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeOfSuperCall.js b/tests/baselines/reference/typeOfSuperCall.js
index 7bad868e33c..9ac69544460 100644
--- a/tests/baselines/reference/typeOfSuperCall.js
+++ b/tests/baselines/reference/typeOfSuperCall.js
@@ -10,7 +10,11 @@ class D extends C {
 
 //// [typeOfSuperCall.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeParameterAsBaseClass.js b/tests/baselines/reference/typeParameterAsBaseClass.js
index 4629854dd37..062ac61fd51 100644
--- a/tests/baselines/reference/typeParameterAsBaseClass.js
+++ b/tests/baselines/reference/typeParameterAsBaseClass.js
@@ -4,7 +4,11 @@ class C2<T> implements T {}
 
 //// [typeParameterAsBaseClass.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeParameterAsBaseType.js b/tests/baselines/reference/typeParameterAsBaseType.js
index 64d0f20c2f0..e77c3b6e0d4 100644
--- a/tests/baselines/reference/typeParameterAsBaseType.js
+++ b/tests/baselines/reference/typeParameterAsBaseType.js
@@ -14,7 +14,11 @@ interface I2<T, U> extends U { }
 // type parameters cannot be used as base types
 // these are all errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeParameterExtendingUnion1.js b/tests/baselines/reference/typeParameterExtendingUnion1.js
index 73efba3f0d7..5d15b09720f 100644
--- a/tests/baselines/reference/typeParameterExtendingUnion1.js
+++ b/tests/baselines/reference/typeParameterExtendingUnion1.js
@@ -14,7 +14,11 @@ function f<T extends Cat | Dog>(a: T) {
 
 //// [typeParameterExtendingUnion1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeParameterExtendingUnion2.js b/tests/baselines/reference/typeParameterExtendingUnion2.js
index 17d8d02cd9a..d274169391f 100644
--- a/tests/baselines/reference/typeParameterExtendingUnion2.js
+++ b/tests/baselines/reference/typeParameterExtendingUnion2.js
@@ -14,7 +14,11 @@ function f<T extends Cat | Dog>(a: T) {
 
 //// [typeParameterExtendingUnion2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeRelationships.js b/tests/baselines/reference/typeRelationships.js
index 0d30916767e..745e2dffe00 100644
--- a/tests/baselines/reference/typeRelationships.js
+++ b/tests/baselines/reference/typeRelationships.js
@@ -42,7 +42,11 @@ class D extends C {
 
 //// [typeRelationships.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeValueConflict1.js b/tests/baselines/reference/typeValueConflict1.js
index 3abbb5cd21b..c66ed5fbfd4 100644
--- a/tests/baselines/reference/typeValueConflict1.js
+++ b/tests/baselines/reference/typeValueConflict1.js
@@ -13,7 +13,11 @@ module M2 {
 
 //// [typeValueConflict1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeValueConflict2.js b/tests/baselines/reference/typeValueConflict2.js
index 604acf71d15..c72115d0dfc 100644
--- a/tests/baselines/reference/typeValueConflict2.js
+++ b/tests/baselines/reference/typeValueConflict2.js
@@ -20,7 +20,11 @@ module M3 {
 
 //// [typeValueConflict2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typeofClass2.js b/tests/baselines/reference/typeofClass2.js
index fb04510e23f..46f9d7dc7f9 100644
--- a/tests/baselines/reference/typeofClass2.js
+++ b/tests/baselines/reference/typeofClass2.js
@@ -23,7 +23,11 @@ var r2: typeof d;
 
 //// [typeofClass2.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typesWithSpecializedCallSignatures.js b/tests/baselines/reference/typesWithSpecializedCallSignatures.js
index e46c2a3c267..d011126edeb 100644
--- a/tests/baselines/reference/typesWithSpecializedCallSignatures.js
+++ b/tests/baselines/reference/typesWithSpecializedCallSignatures.js
@@ -44,7 +44,11 @@ var r3: Base = c.foo('hm');
 //// [typesWithSpecializedCallSignatures.js]
 // basic uses of specialized signatures without errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/typesWithSpecializedConstructSignatures.js b/tests/baselines/reference/typesWithSpecializedConstructSignatures.js
index 37fc51c3f3a..79cd99f249d 100644
--- a/tests/baselines/reference/typesWithSpecializedConstructSignatures.js
+++ b/tests/baselines/reference/typesWithSpecializedConstructSignatures.js
@@ -42,7 +42,11 @@ var r3: Base = new a('hm');
 //// [typesWithSpecializedConstructSignatures.js]
 // basic uses of specialized signatures without errors
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/undeclaredBase.js b/tests/baselines/reference/undeclaredBase.js
index 3d07bc89571..a96a892e9a2 100644
--- a/tests/baselines/reference/undeclaredBase.js
+++ b/tests/baselines/reference/undeclaredBase.js
@@ -5,7 +5,11 @@ module M { export class C extends M.I { } }
 
 //// [undeclaredBase.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/undefinedIsSubtypeOfEverything.js b/tests/baselines/reference/undefinedIsSubtypeOfEverything.js
index 393c5e24544..aa4fac8d6eb 100644
--- a/tests/baselines/reference/undefinedIsSubtypeOfEverything.js
+++ b/tests/baselines/reference/undefinedIsSubtypeOfEverything.js
@@ -124,7 +124,11 @@ class D17 extends Base {
 //// [undefinedIsSubtypeOfEverything.js]
 // undefined is a subtype of every other types, no errors expected below
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/underscoreMapFirst.js b/tests/baselines/reference/underscoreMapFirst.js
index 3edb48cd2d1..4f3990b7b57 100644
--- a/tests/baselines/reference/underscoreMapFirst.js
+++ b/tests/baselines/reference/underscoreMapFirst.js
@@ -50,7 +50,11 @@ class MyView extends View {
 
 //// [underscoreMapFirst.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass01.js b/tests/baselines/reference/underscoreThisInDerivedClass01.js
index c7f30f0ec87..439c33df0ec 100644
--- a/tests/baselines/reference/underscoreThisInDerivedClass01.js
+++ b/tests/baselines/reference/underscoreThisInDerivedClass01.js
@@ -26,7 +26,11 @@ class D extends C {
 //// [underscoreThisInDerivedClass01.js]
 // @target es5
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass02.js b/tests/baselines/reference/underscoreThisInDerivedClass02.js
index 89d3bf5a4f9..26f2796e4b0 100644
--- a/tests/baselines/reference/underscoreThisInDerivedClass02.js
+++ b/tests/baselines/reference/underscoreThisInDerivedClass02.js
@@ -20,7 +20,11 @@ class D extends C {
 //// [underscoreThisInDerivedClass02.js]
 // @target es5
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unionTypeEquivalence.js b/tests/baselines/reference/unionTypeEquivalence.js
index bcb1f28f12b..1cafbc8d65c 100644
--- a/tests/baselines/reference/unionTypeEquivalence.js
+++ b/tests/baselines/reference/unionTypeEquivalence.js
@@ -21,7 +21,11 @@ var z1: string | typeof BC;
 
 //// [unionTypeEquivalence.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unionTypeFromArrayLiteral.js b/tests/baselines/reference/unionTypeFromArrayLiteral.js
index a908067574f..12d524f8616 100644
--- a/tests/baselines/reference/unionTypeFromArrayLiteral.js
+++ b/tests/baselines/reference/unionTypeFromArrayLiteral.js
@@ -29,7 +29,11 @@ var arr9 = [e, f]; // (E|F)[]
 // Otherwise, if the array literal is contextually typed by a type that has a property with the numeric name ‘0’, the resulting type is a tuple type constructed from the types of the element expressions.
 // Otherwise, the resulting type is an array type with an element type that is the union of the types of the element expressions.
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unionTypesAssignability.js b/tests/baselines/reference/unionTypesAssignability.js
index 38c991bed61..bf5c69f93e9 100644
--- a/tests/baselines/reference/unionTypesAssignability.js
+++ b/tests/baselines/reference/unionTypesAssignability.js
@@ -75,7 +75,11 @@ function foo<T, U>(t: T, u: U) {
 
 //// [unionTypesAssignability.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unknownSymbols1.js b/tests/baselines/reference/unknownSymbols1.js
index 9fed0f3a716..3768213892a 100644
--- a/tests/baselines/reference/unknownSymbols1.js
+++ b/tests/baselines/reference/unknownSymbols1.js
@@ -34,7 +34,11 @@ class C5 {
 
 //// [unknownSymbols1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unspecializedConstraints.js b/tests/baselines/reference/unspecializedConstraints.js
index e4c102d882d..fbb4c157665 100644
--- a/tests/baselines/reference/unspecializedConstraints.js
+++ b/tests/baselines/reference/unspecializedConstraints.js
@@ -155,7 +155,11 @@ module ts {
 
 //// [unspecializedConstraints.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/untypedFunctionCallsWithTypeParameters1.js b/tests/baselines/reference/untypedFunctionCallsWithTypeParameters1.js
index a651fdf7e8e..67e3d579dc4 100644
--- a/tests/baselines/reference/untypedFunctionCallsWithTypeParameters1.js
+++ b/tests/baselines/reference/untypedFunctionCallsWithTypeParameters1.js
@@ -45,7 +45,11 @@ c5<string>(1); // error
 
 //// [untypedFunctionCallsWithTypeParameters1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unusedClassesinNamespace4.js b/tests/baselines/reference/unusedClassesinNamespace4.js
index bf5e996d2d2..af2c9d96f52 100644
--- a/tests/baselines/reference/unusedClassesinNamespace4.js
+++ b/tests/baselines/reference/unusedClassesinNamespace4.js
@@ -16,7 +16,11 @@ namespace Validation {
 
 //// [unusedClassesinNamespace4.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/unusedIdentifiersConsolidated1.js b/tests/baselines/reference/unusedIdentifiersConsolidated1.js
index 6419fbe250b..7bea43688ad 100644
--- a/tests/baselines/reference/unusedIdentifiersConsolidated1.js
+++ b/tests/baselines/reference/unusedIdentifiersConsolidated1.js
@@ -104,7 +104,11 @@ namespace Greeter {
 
 //// [unusedIdentifiersConsolidated1.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/validUseOfThisInSuper.js b/tests/baselines/reference/validUseOfThisInSuper.js
index b5eecf1720d..b32d9413bdf 100644
--- a/tests/baselines/reference/validUseOfThisInSuper.js
+++ b/tests/baselines/reference/validUseOfThisInSuper.js
@@ -11,7 +11,11 @@ class Super extends Base {
 
 //// [validUseOfThisInSuper.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };
diff --git a/tests/baselines/reference/varArgsOnConstructorTypes.js b/tests/baselines/reference/varArgsOnConstructorTypes.js
index 547260c6197..f9674ceb328 100644
--- a/tests/baselines/reference/varArgsOnConstructorTypes.js
+++ b/tests/baselines/reference/varArgsOnConstructorTypes.js
@@ -26,7 +26,11 @@ reg.register(B);
 
 //// [varArgsOnConstructorTypes.js]
 var __extends = (this && this.__extends) || function (d, b) {
-    Object.setPrototypeOf(d, b);
+    if (typeof Object.setPrototypeOf === "function") {
+        Object.setPrototypeOf(d, b);
+    } else {
+        d.__proto__ = b;
+    }
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };