diff --git a/src/compiler/transformers/module/module.ts b/src/compiler/transformers/module/module.ts
index 1568f17ecf7..7e0d1685d18 100644
--- a/src/compiler/transformers/module/module.ts
+++ b/src/compiler/transformers/module/module.ts
@@ -665,14 +665,9 @@ namespace ts {
 
         function visitExpressionStatement(node: ExpressionStatement): VisitResult<Statement> {
             const original = getOriginalNode(node);
-            if (hasModifier(original, ModifierFlags.Export)) {
-                switch (original.kind) {
-                    case SyntaxKind.EnumDeclaration:
-                        return visitExpressionStatementForEnumDeclaration(node, <EnumDeclaration>original);
-
-                    case SyntaxKind.ModuleDeclaration:
-                        return visitExpressionStatementForModuleDeclaration(node, <ModuleDeclaration>original);
-                }
+            if (original.kind === SyntaxKind.EnumDeclaration
+                && hasModifier(original, ModifierFlags.Export)) {
+                return visitExpressionStatementForEnumDeclaration(node, <EnumDeclaration>original);
             }
 
             return node;
@@ -681,28 +676,7 @@ namespace ts {
         function visitExpressionStatementForEnumDeclaration(node: ExpressionStatement, original: EnumDeclaration): VisitResult<Statement> {
             if (isFirstDeclarationOfKind(original, SyntaxKind.EnumDeclaration)) {
                 const statements: Statement[] = [node];
-                addVarForExportedEnumOrModule(statements, original);
-                return statements;
-            }
-
-            return node;
-        }
-
-        function isModuleMergedWithES6Class(node: ModuleDeclaration) {
-            return languageVersion === ScriptTarget.ES6
-                && isMergedWithClass(node);
-        }
-
-        function visitExpressionStatementForModuleDeclaration(node: ExpressionStatement, original: ModuleDeclaration): VisitResult<Statement> {
-            if (isFirstDeclarationOfKind(original, SyntaxKind.ModuleDeclaration)) {
-                const statements: Statement[] = [node];
-                if (isModuleMergedWithES6Class(original)) {
-                    addAssignmentForExportedModule(statements, original);
-                }
-                else {
-                    addVarForExportedEnumOrModule(statements, original);
-                }
-
+                addVarForExportedEnumDeclaration(statements, original);
                 return statements;
             }
 
@@ -712,7 +686,7 @@ namespace ts {
         /**
          * Adds a trailing VariableStatement for an enum or module declaration.
          */
-        function addVarForExportedEnumOrModule(statements: Statement[], node: EnumDeclaration | ModuleDeclaration) {
+        function addVarForExportedEnumDeclaration(statements: Statement[], node: EnumDeclaration | ModuleDeclaration) {
             statements.push(
                 createVariableStatement(
                     /*modifiers*/ undefined,
@@ -725,21 +699,6 @@ namespace ts {
             );
         }
 
-        /**
-         * Adds a trailing assignment for a module declaration.
-         */
-        function addAssignmentForExportedModule(statements: Statement[], node: ModuleDeclaration) {
-            statements.push(
-                createStatement(
-                    createAssignment(
-                        getDeclarationName(node),
-                        createPropertyAccess(createIdentifier("exports"), getDeclarationName(node))
-                    ),
-                    /*location*/ node
-                )
-            );
-        }
-
         function getDeclarationName(node: DeclarationStatement) {
             return node.name ? getSynthesizedClone(node.name) : getGeneratedNameForNode(node);
         }
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index 968ac152065..b9f10f21330 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -27,6 +27,7 @@ namespace ts {
         const resolver = context.getEmitResolver();
         const compilerOptions = context.getCompilerOptions();
         const languageVersion = getEmitScriptTarget(compilerOptions);
+        const moduleKind = getEmitModuleKind(compilerOptions);
 
         // Save the previous transformation hooks.
         const previousOnEmitNode = context.onEmitNode;
@@ -2167,14 +2168,32 @@ namespace ts {
             return createPartiallyEmittedExpression(expression, node);
         }
 
+        /**
+         * Determines whether to emit an enum declaration.
+         *
+         * @param node The enum declaration node.
+         */
+        function shouldEmitEnumDeclaration(node: EnumDeclaration) {
+            return !isConst(node)
+                || compilerOptions.preserveConstEnums
+                || compilerOptions.isolatedModules;
+        }
+
+        function shouldEmitVarForEnumDeclaration(node: EnumDeclaration | ModuleDeclaration) {
+            return !hasModifier(node, ModifierFlags.Export)
+                || (isES6ExportedDeclaration(node) && isFirstDeclarationOfKind(node, node.kind));
+        }
+
         /**
          * Adds a leading VariableStatement for an enum or module declaration.
          */
-        function addVarForEnumOrModuleDeclaration(statements: Statement[], node: EnumDeclaration | ModuleDeclaration) {
+        function addVarForEnumDeclaration(statements: Statement[], node: EnumDeclaration) {
             // Emit a variable statement for the enum.
             statements.push(
                 createVariableStatement(
-                    visitNodes(node.modifiers, visitor, isModifier),
+                    isES6ExportedDeclaration(node)
+                        ? visitNodes(node.modifiers, visitor, isModifier)
+                        : undefined,
                     [createVariableDeclaration(
                         getDeclarationName(node)
                     )],
@@ -2186,7 +2205,7 @@ namespace ts {
         /**
          * Adds a trailing VariableStatement for an enum or module declaration.
          */
-        function addVarForEnumOrModuleExportedFromNamespace(statements: Statement[], node: EnumDeclaration | ModuleDeclaration) {
+        function addVarForEnumExportedFromNamespace(statements: Statement[], node: EnumDeclaration | ModuleDeclaration) {
             statements.push(
                 createVariableStatement(
                     /*modifiers*/ undefined,
@@ -2199,34 +2218,6 @@ namespace ts {
             )
         }
 
-        function addAssignmentForModuleExportedFromNamespace(statements: Statement[], node: ModuleDeclaration) {
-            statements.push(
-                createStatement(
-                    createAssignment(
-                        getDeclarationName(node),
-                        setNodeEmitFlags(getDeclarationName(node), NodeEmitFlags.PrefixExportedLocal)
-                    ),
-                    /*location*/ node
-                )
-            );
-        }
-
-        /**
-         * Determines whether to emit an enum declaration.
-         *
-         * @param node The enum declaration node.
-         */
-        function shouldEmitEnumDeclaration(node: EnumDeclaration) {
-            return !isConst(node)
-                || compilerOptions.preserveConstEnums
-                || compilerOptions.isolatedModules;
-        }
-
-        function shouldEmitVarForEnumOrModuleDeclaration(node: EnumDeclaration | ModuleDeclaration) {
-            return !hasModifier(node, ModifierFlags.Export)
-                || (isExternalModuleExport(node) && isFirstDeclarationOfKind(node, node.kind));
-        }
-
         /**
          * Visits an enum declaration.
          *
@@ -2240,8 +2231,8 @@ namespace ts {
             }
 
             const statements: Statement[] = [];
-            if (shouldEmitVarForEnumOrModuleDeclaration(node)) {
-                addVarForEnumOrModuleDeclaration(statements, node);
+            if (shouldEmitVarForEnumDeclaration(node)) {
+                addVarForEnumDeclaration(statements, node);
             }
 
             const localName = getGeneratedNameForNode(node);
@@ -2276,7 +2267,7 @@ namespace ts {
             );
 
             if (isNamespaceExport(node)) {
-                addVarForEnumOrModuleExportedFromNamespace(statements, node);
+                addVarForEnumExportedFromNamespace(statements, node);
             }
 
             return statements;
@@ -2357,6 +2348,38 @@ namespace ts {
                 && isMergedWithClass(node);
         }
 
+        function isES6ExportedDeclaration(node: Node) {
+            return isExternalModuleExport(node)
+                && moduleKind >= ModuleKind.ES6;
+        }
+
+        function shouldEmitVarForModuleDeclaration(node: ModuleDeclaration) {
+            return !isModuleMergedWithES6Class(node)
+                && (!isES6ExportedDeclaration(node)
+                    || isFirstDeclarationOfKind(node, node.kind));
+        }
+
+        /**
+         * Adds a leading VariableStatement for a module declaration.
+         */
+        function addVarForModuleDeclaration(statements: Statement[], node: ModuleDeclaration) {
+            // Emit a variable statement for the module.
+            statements.push(
+                setOriginalNode(
+                    createVariableStatement(
+                        isES6ExportedDeclaration(node)
+                            ? visitNodes(node.modifiers, visitor, isModifier)
+                            : undefined,
+                        [createVariableDeclaration(
+                            getDeclarationName(node)
+                        )],
+                        /*location*/ node
+                    ),
+                    node
+                )
+            );
+        }
+
         /**
          * Visits a module declaration node.
          *
@@ -2373,8 +2396,9 @@ namespace ts {
             enableExpressionSubstitutionForNamespaceExports();
 
             const statements: Statement[] = [];
-            if (!isModuleMergedWithES6Class(node) && (isNamespaceExport(node) || shouldEmitVarForEnumOrModuleDeclaration(node))) {
-                addVarForEnumOrModuleDeclaration(statements, node);
+
+            if (shouldEmitVarForModuleDeclaration(node)) {
+                addVarForModuleDeclaration(statements, node);
             }
 
             const localName = getGeneratedNameForNode(node);
@@ -2389,7 +2413,7 @@ namespace ts {
                     )
                 );
 
-            if (isNamespaceExport(node)) {
+            if (hasModifier(node, ModifierFlags.Export) && !isES6ExportedDeclaration(node)) {
                 moduleArg = createAssignment(getDeclarationName(node), moduleArg);
             }