diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index d7996238f4c..71074c53d9c 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -4377,15 +4377,18 @@ var __param = (this && this.__param) || function (paramIndex, decorator) {
                     return;
                 }
 
-                if (!(node.flags & NodeFlags.Export) || isES6ExportedDeclaration(node)) {
-                    emitStart(node);
-                    if (isES6ExportedDeclaration(node)) {
-                        write("export ");
+                if (!shouldHoistDeclarationInSystemJsModule(node)) {
+                    // do not emit var if variable was already hoisted
+                    if (!(node.flags & NodeFlags.Export) || isES6ExportedDeclaration(node)) {
+                        emitStart(node);
+                        if (isES6ExportedDeclaration(node)) {
+                            write("export ");
+                        }
+                        write("var ");
+                        emit(node.name);
+                        emitEnd(node);
+                        write(";");
                     }
-                    write("var ");
-                    emit(node.name);
-                    emitEnd(node);
-                    write(";");
                 }
                 writeLine();
                 emitStart(node);
diff --git a/tests/baselines/reference/systemModuleConstEnums.js b/tests/baselines/reference/systemModuleConstEnums.js
new file mode 100644
index 00000000000..126e6266b2c
--- /dev/null
+++ b/tests/baselines/reference/systemModuleConstEnums.js
@@ -0,0 +1,27 @@
+//// [systemModuleConstEnums.ts]
+
+declare function use(a: any);
+const enum TopLevelConstEnum { X }
+
+export function foo() {
+    use(TopLevelConstEnum.X);
+    use(M.NonTopLevelConstEnum.X);
+}
+
+module M {
+    export const enum NonTopLevelConstEnum { X }
+}
+
+//// [systemModuleConstEnums.js]
+System.register([], function(exports_1) {
+    function foo() {
+        use(0 /* X */);
+        use(0 /* X */);
+    }
+    exports_1("foo", foo);
+    return {
+        setters:[],
+        execute: function() {
+        }
+    }
+});
diff --git a/tests/baselines/reference/systemModuleConstEnums.symbols b/tests/baselines/reference/systemModuleConstEnums.symbols
new file mode 100644
index 00000000000..171f24628ec
--- /dev/null
+++ b/tests/baselines/reference/systemModuleConstEnums.symbols
@@ -0,0 +1,35 @@
+=== tests/cases/compiler/systemModuleConstEnums.ts ===
+
+declare function use(a: any);
+>use : Symbol(use, Decl(systemModuleConstEnums.ts, 0, 0))
+>a : Symbol(a, Decl(systemModuleConstEnums.ts, 1, 21))
+
+const enum TopLevelConstEnum { X }
+>TopLevelConstEnum : Symbol(TopLevelConstEnum, Decl(systemModuleConstEnums.ts, 1, 29))
+>X : Symbol(TopLevelConstEnum.X, Decl(systemModuleConstEnums.ts, 2, 30))
+
+export function foo() {
+>foo : Symbol(foo, Decl(systemModuleConstEnums.ts, 2, 34))
+
+    use(TopLevelConstEnum.X);
+>use : Symbol(use, Decl(systemModuleConstEnums.ts, 0, 0))
+>TopLevelConstEnum.X : Symbol(TopLevelConstEnum.X, Decl(systemModuleConstEnums.ts, 2, 30))
+>TopLevelConstEnum : Symbol(TopLevelConstEnum, Decl(systemModuleConstEnums.ts, 1, 29))
+>X : Symbol(TopLevelConstEnum.X, Decl(systemModuleConstEnums.ts, 2, 30))
+
+    use(M.NonTopLevelConstEnum.X);
+>use : Symbol(use, Decl(systemModuleConstEnums.ts, 0, 0))
+>M.NonTopLevelConstEnum.X : Symbol(M.NonTopLevelConstEnum.X, Decl(systemModuleConstEnums.ts, 10, 44))
+>M.NonTopLevelConstEnum : Symbol(M.NonTopLevelConstEnum, Decl(systemModuleConstEnums.ts, 9, 10))
+>M : Symbol(M, Decl(systemModuleConstEnums.ts, 7, 1))
+>NonTopLevelConstEnum : Symbol(M.NonTopLevelConstEnum, Decl(systemModuleConstEnums.ts, 9, 10))
+>X : Symbol(M.NonTopLevelConstEnum.X, Decl(systemModuleConstEnums.ts, 10, 44))
+}
+
+module M {
+>M : Symbol(M, Decl(systemModuleConstEnums.ts, 7, 1))
+
+    export const enum NonTopLevelConstEnum { X }
+>NonTopLevelConstEnum : Symbol(NonTopLevelConstEnum, Decl(systemModuleConstEnums.ts, 9, 10))
+>X : Symbol(NonTopLevelConstEnum.X, Decl(systemModuleConstEnums.ts, 10, 44))
+}
diff --git a/tests/baselines/reference/systemModuleConstEnums.types b/tests/baselines/reference/systemModuleConstEnums.types
new file mode 100644
index 00000000000..193de0da3ab
--- /dev/null
+++ b/tests/baselines/reference/systemModuleConstEnums.types
@@ -0,0 +1,37 @@
+=== tests/cases/compiler/systemModuleConstEnums.ts ===
+
+declare function use(a: any);
+>use : (a: any) => any
+>a : any
+
+const enum TopLevelConstEnum { X }
+>TopLevelConstEnum : TopLevelConstEnum
+>X : TopLevelConstEnum
+
+export function foo() {
+>foo : () => void
+
+    use(TopLevelConstEnum.X);
+>use(TopLevelConstEnum.X) : any
+>use : (a: any) => any
+>TopLevelConstEnum.X : TopLevelConstEnum
+>TopLevelConstEnum : typeof TopLevelConstEnum
+>X : TopLevelConstEnum
+
+    use(M.NonTopLevelConstEnum.X);
+>use(M.NonTopLevelConstEnum.X) : any
+>use : (a: any) => any
+>M.NonTopLevelConstEnum.X : M.NonTopLevelConstEnum
+>M.NonTopLevelConstEnum : typeof M.NonTopLevelConstEnum
+>M : typeof M
+>NonTopLevelConstEnum : typeof M.NonTopLevelConstEnum
+>X : M.NonTopLevelConstEnum
+}
+
+module M {
+>M : typeof M
+
+    export const enum NonTopLevelConstEnum { X }
+>NonTopLevelConstEnum : NonTopLevelConstEnum
+>X : NonTopLevelConstEnum
+}
diff --git a/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.js b/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.js
new file mode 100644
index 00000000000..381331a84db
--- /dev/null
+++ b/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.js
@@ -0,0 +1,37 @@
+//// [systemModuleConstEnumsSeparateCompilation.ts]
+
+declare function use(a: any);
+const enum TopLevelConstEnum { X }
+
+export function foo() {
+    use(TopLevelConstEnum.X);
+    use(M.NonTopLevelConstEnum.X);
+}
+
+module M {
+    export const enum NonTopLevelConstEnum { X }
+}
+
+//// [systemModuleConstEnumsSeparateCompilation.js]
+System.register([], function(exports_1) {
+    var TopLevelConstEnum, M;
+    function foo() {
+        use(TopLevelConstEnum.X);
+        use(M.NonTopLevelConstEnum.X);
+    }
+    exports_1("foo", foo);
+    return {
+        setters:[],
+        execute: function() {
+            (function (TopLevelConstEnum) {
+                TopLevelConstEnum[TopLevelConstEnum["X"] = 0] = "X";
+            })(TopLevelConstEnum || (TopLevelConstEnum = {}));
+            (function (M) {
+                (function (NonTopLevelConstEnum) {
+                    NonTopLevelConstEnum[NonTopLevelConstEnum["X"] = 0] = "X";
+                })(M.NonTopLevelConstEnum || (M.NonTopLevelConstEnum = {}));
+                var NonTopLevelConstEnum = M.NonTopLevelConstEnum;
+            })(M || (M = {}));
+        }
+    }
+});
diff --git a/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.symbols b/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.symbols
new file mode 100644
index 00000000000..d57740b75e9
--- /dev/null
+++ b/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.symbols
@@ -0,0 +1,35 @@
+=== tests/cases/compiler/systemModuleConstEnumsSeparateCompilation.ts ===
+
+declare function use(a: any);
+>use : Symbol(use, Decl(systemModuleConstEnumsSeparateCompilation.ts, 0, 0))
+>a : Symbol(a, Decl(systemModuleConstEnumsSeparateCompilation.ts, 1, 21))
+
+const enum TopLevelConstEnum { X }
+>TopLevelConstEnum : Symbol(TopLevelConstEnum, Decl(systemModuleConstEnumsSeparateCompilation.ts, 1, 29))
+>X : Symbol(TopLevelConstEnum.X, Decl(systemModuleConstEnumsSeparateCompilation.ts, 2, 30))
+
+export function foo() {
+>foo : Symbol(foo, Decl(systemModuleConstEnumsSeparateCompilation.ts, 2, 34))
+
+    use(TopLevelConstEnum.X);
+>use : Symbol(use, Decl(systemModuleConstEnumsSeparateCompilation.ts, 0, 0))
+>TopLevelConstEnum.X : Symbol(TopLevelConstEnum.X, Decl(systemModuleConstEnumsSeparateCompilation.ts, 2, 30))
+>TopLevelConstEnum : Symbol(TopLevelConstEnum, Decl(systemModuleConstEnumsSeparateCompilation.ts, 1, 29))
+>X : Symbol(TopLevelConstEnum.X, Decl(systemModuleConstEnumsSeparateCompilation.ts, 2, 30))
+
+    use(M.NonTopLevelConstEnum.X);
+>use : Symbol(use, Decl(systemModuleConstEnumsSeparateCompilation.ts, 0, 0))
+>M.NonTopLevelConstEnum.X : Symbol(M.NonTopLevelConstEnum.X, Decl(systemModuleConstEnumsSeparateCompilation.ts, 10, 44))
+>M.NonTopLevelConstEnum : Symbol(M.NonTopLevelConstEnum, Decl(systemModuleConstEnumsSeparateCompilation.ts, 9, 10))
+>M : Symbol(M, Decl(systemModuleConstEnumsSeparateCompilation.ts, 7, 1))
+>NonTopLevelConstEnum : Symbol(M.NonTopLevelConstEnum, Decl(systemModuleConstEnumsSeparateCompilation.ts, 9, 10))
+>X : Symbol(M.NonTopLevelConstEnum.X, Decl(systemModuleConstEnumsSeparateCompilation.ts, 10, 44))
+}
+
+module M {
+>M : Symbol(M, Decl(systemModuleConstEnumsSeparateCompilation.ts, 7, 1))
+
+    export const enum NonTopLevelConstEnum { X }
+>NonTopLevelConstEnum : Symbol(NonTopLevelConstEnum, Decl(systemModuleConstEnumsSeparateCompilation.ts, 9, 10))
+>X : Symbol(NonTopLevelConstEnum.X, Decl(systemModuleConstEnumsSeparateCompilation.ts, 10, 44))
+}
diff --git a/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.types b/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.types
new file mode 100644
index 00000000000..c3a352f66ec
--- /dev/null
+++ b/tests/baselines/reference/systemModuleConstEnumsSeparateCompilation.types
@@ -0,0 +1,37 @@
+=== tests/cases/compiler/systemModuleConstEnumsSeparateCompilation.ts ===
+
+declare function use(a: any);
+>use : (a: any) => any
+>a : any
+
+const enum TopLevelConstEnum { X }
+>TopLevelConstEnum : TopLevelConstEnum
+>X : TopLevelConstEnum
+
+export function foo() {
+>foo : () => void
+
+    use(TopLevelConstEnum.X);
+>use(TopLevelConstEnum.X) : any
+>use : (a: any) => any
+>TopLevelConstEnum.X : TopLevelConstEnum
+>TopLevelConstEnum : typeof TopLevelConstEnum
+>X : TopLevelConstEnum
+
+    use(M.NonTopLevelConstEnum.X);
+>use(M.NonTopLevelConstEnum.X) : any
+>use : (a: any) => any
+>M.NonTopLevelConstEnum.X : M.NonTopLevelConstEnum
+>M.NonTopLevelConstEnum : typeof M.NonTopLevelConstEnum
+>M : typeof M
+>NonTopLevelConstEnum : typeof M.NonTopLevelConstEnum
+>X : M.NonTopLevelConstEnum
+}
+
+module M {
+>M : typeof M
+
+    export const enum NonTopLevelConstEnum { X }
+>NonTopLevelConstEnum : NonTopLevelConstEnum
+>X : NonTopLevelConstEnum
+}
diff --git a/tests/baselines/reference/systemModuleExportDefault.js b/tests/baselines/reference/systemModuleExportDefault.js
new file mode 100644
index 00000000000..4df3ec828c1
--- /dev/null
+++ b/tests/baselines/reference/systemModuleExportDefault.js
@@ -0,0 +1,67 @@
+//// [tests/cases/compiler/systemModuleExportDefault.ts] ////
+
+//// [file1.ts]
+
+export default function() {}
+
+//// [file2.ts]
+export default function foo() {}
+
+//// [file3.ts]
+export default class {}
+
+//// [file4.ts]
+export default class C {}
+
+
+
+//// [file1.js]
+System.register([], function(exports_1) {
+    function default_1() { }
+    exports_1("default", default_1);
+    return {
+        setters:[],
+        execute: function() {
+        }
+    }
+});
+//// [file2.js]
+System.register([], function(exports_1) {
+    function foo() { }
+    exports_1("default", foo);
+    return {
+        setters:[],
+        execute: function() {
+        }
+    }
+});
+//// [file3.js]
+System.register([], function(exports_1) {
+    var default_1;
+    return {
+        setters:[],
+        execute: function() {
+            default_1 = (function () {
+                function default_1() {
+                }
+                return default_1;
+            })();
+            exports_1("default", default_1);
+        }
+    }
+});
+//// [file4.js]
+System.register([], function(exports_1) {
+    var C;
+    return {
+        setters:[],
+        execute: function() {
+            C = (function () {
+                function C() {
+                }
+                return C;
+            })();
+            exports_1("default", C);
+        }
+    }
+});
diff --git a/tests/baselines/reference/systemModuleExportDefault.symbols b/tests/baselines/reference/systemModuleExportDefault.symbols
new file mode 100644
index 00000000000..d6e7cde9b71
--- /dev/null
+++ b/tests/baselines/reference/systemModuleExportDefault.symbols
@@ -0,0 +1,16 @@
+=== tests/cases/compiler/file1.ts ===
+
+No type information for this code.export default function() {}
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/file2.ts ===
+export default function foo() {}
+>foo : Symbol(foo, Decl(file2.ts, 0, 0))
+
+=== tests/cases/compiler/file3.ts ===
+export default class {}
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/file4.ts ===
+export default class C {}
+>C : Symbol(C, Decl(file4.ts, 0, 0))
+
+
diff --git a/tests/baselines/reference/systemModuleExportDefault.types b/tests/baselines/reference/systemModuleExportDefault.types
new file mode 100644
index 00000000000..38b5abec8ed
--- /dev/null
+++ b/tests/baselines/reference/systemModuleExportDefault.types
@@ -0,0 +1,16 @@
+=== tests/cases/compiler/file1.ts ===
+
+No type information for this code.export default function() {}
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/file2.ts ===
+export default function foo() {}
+>foo : () => void
+
+=== tests/cases/compiler/file3.ts ===
+export default class {}
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/file4.ts ===
+export default class C {}
+>C : C
+
+
diff --git a/tests/cases/compiler/systemModuleConstEnums.ts b/tests/cases/compiler/systemModuleConstEnums.ts
new file mode 100644
index 00000000000..6ad7f31ef91
--- /dev/null
+++ b/tests/cases/compiler/systemModuleConstEnums.ts
@@ -0,0 +1,13 @@
+// @module: system
+
+declare function use(a: any);
+const enum TopLevelConstEnum { X }
+
+export function foo() {
+    use(TopLevelConstEnum.X);
+    use(M.NonTopLevelConstEnum.X);
+}
+
+module M {
+    export const enum NonTopLevelConstEnum { X }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/systemModuleConstEnumsSeparateCompilation.ts b/tests/cases/compiler/systemModuleConstEnumsSeparateCompilation.ts
new file mode 100644
index 00000000000..2fc4707b78e
--- /dev/null
+++ b/tests/cases/compiler/systemModuleConstEnumsSeparateCompilation.ts
@@ -0,0 +1,14 @@
+// @module: system
+// @separateCompilation: true
+
+declare function use(a: any);
+const enum TopLevelConstEnum { X }
+
+export function foo() {
+    use(TopLevelConstEnum.X);
+    use(M.NonTopLevelConstEnum.X);
+}
+
+module M {
+    export const enum NonTopLevelConstEnum { X }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/systemModuleExportDefault.ts b/tests/cases/compiler/systemModuleExportDefault.ts
new file mode 100644
index 00000000000..102c03f0bcd
--- /dev/null
+++ b/tests/cases/compiler/systemModuleExportDefault.ts
@@ -0,0 +1,14 @@
+// @module: system
+
+// @filename: file1.ts
+export default function() {}
+
+// @filename: file2.ts
+export default function foo() {}
+
+// @filename: file3.ts
+export default class {}
+
+// @filename: file4.ts
+export default class C {}
+