diff --git a/src/compiler/transformers/declarations.ts b/src/compiler/transformers/declarations.ts
index 15d7cb6ff5fa5..20aac7d4936e5 100644
--- a/src/compiler/transformers/declarations.ts
+++ b/src/compiler/transformers/declarations.ts
@@ -63,7 +63,7 @@ namespace ts {
         let enclosingDeclaration: Node;
         let necessaryTypeReferences: Map<true> | undefined;
         let lateMarkedStatements: LateVisibilityPaintedStatement[] | undefined;
-        let lateStatementReplacementMap: Map<VisitResult<LateVisibilityPaintedStatement>>;
+        let lateStatementReplacementMap: Map<VisitResult<LateVisibilityPaintedStatement | ExportAssignment>>;
         let suppressNewDiagnosticContexts: boolean;
         let exportedModulesFromDeclarationEmit: Symbol[] | undefined;
 
@@ -701,12 +701,12 @@ namespace ts {
             }
         }
 
-        function isExternalModuleIndicator(result: LateVisibilityPaintedStatement) {
+        function isExternalModuleIndicator(result: LateVisibilityPaintedStatement | ExportAssignment) {
             // Exported top-level member indicates moduleness
             return isAnyImportOrReExport(result) || isExportAssignment(result) || hasModifier(result, ModifierFlags.Export);
         }
 
-        function needsScopeMarker(result: LateVisibilityPaintedStatement) {
+        function needsScopeMarker(result: LateVisibilityPaintedStatement | ExportAssignment) {
             return !isAnyImportOrReExport(result) && !isExportAssignment(result) && !hasModifier(result, ModifierFlags.Export) && !isAmbientModule(result);
         }
 
@@ -1047,7 +1047,43 @@ namespace ts {
                             return createVariableStatement(/*modifiers*/ undefined, createVariableDeclarationList([varDecl]));
                         });
                         const namespaceDecl = createModuleDeclaration(/*decorators*/ undefined, ensureModifiers(input, isPrivate), input.name!, createModuleBlock(declarations), NodeFlags.Namespace);
-                        return [clean, namespaceDecl];
+
+                        if (!hasModifier(clean, ModifierFlags.ExportDefault)) {
+                            return [clean, namespaceDecl];
+                        }
+
+                        const modifiers = createModifiersFromModifierFlags((getModifierFlags(clean) & ~ModifierFlags.ExportDefault) | ModifierFlags.Ambient);
+                        const cleanDeclaration = updateFunctionDeclaration(
+                            clean,
+                            /*decorators*/ undefined,
+                            modifiers,
+                            /*asteriskToken*/ undefined,
+                            clean.name,
+                            clean.typeParameters,
+                            clean.parameters,
+                            clean.type,
+                            /*body*/ undefined
+                        );
+
+                        const namespaceDeclaration = updateModuleDeclaration(
+                            namespaceDecl,
+                            /*decorators*/ undefined,
+                            modifiers,
+                            namespaceDecl.name,
+                            namespaceDecl.body
+                        );
+
+                        const exportDefaultDeclaration = createExportAssignment(
+                            /*decorators*/ undefined,
+                            /*modifiers*/ undefined,
+                            /*isExportEquals*/ false,
+                            namespaceDecl.name
+                        );
+
+                        resultHasExternalModuleIndicator = true;
+                        resultHasScopeMarker = true;
+
+                        return [cleanDeclaration, namespaceDeclaration, exportDefaultDeclaration];
                     }
                     else {
                         return clean;
diff --git a/tests/baselines/reference/exportDefaultNamespace.js b/tests/baselines/reference/exportDefaultNamespace.js
new file mode 100644
index 0000000000000..39a70d5e231d7
--- /dev/null
+++ b/tests/baselines/reference/exportDefaultNamespace.js
@@ -0,0 +1,24 @@
+//// [exportDefaultNamespace.ts]
+export default function someFunc() {
+    return 'hello!';
+}
+
+someFunc.someProp = 'yo';
+
+
+//// [exportDefaultNamespace.js]
+"use strict";
+exports.__esModule = true;
+function someFunc() {
+    return 'hello!';
+}
+exports["default"] = someFunc;
+someFunc.someProp = 'yo';
+
+
+//// [exportDefaultNamespace.d.ts]
+declare function someFunc(): string;
+declare namespace someFunc {
+    var someProp: string;
+}
+export default someFunc;
diff --git a/tests/baselines/reference/exportDefaultNamespace.symbols b/tests/baselines/reference/exportDefaultNamespace.symbols
new file mode 100644
index 0000000000000..eee148768948b
--- /dev/null
+++ b/tests/baselines/reference/exportDefaultNamespace.symbols
@@ -0,0 +1,12 @@
+=== tests/cases/conformance/declarationEmit/exportDefaultNamespace.ts ===
+export default function someFunc() {
+>someFunc : Symbol(someFunc, Decl(exportDefaultNamespace.ts, 0, 0), Decl(exportDefaultNamespace.ts, 2, 1))
+
+    return 'hello!';
+}
+
+someFunc.someProp = 'yo';
+>someFunc.someProp : Symbol(someFunc.someProp, Decl(exportDefaultNamespace.ts, 2, 1))
+>someFunc : Symbol(someFunc, Decl(exportDefaultNamespace.ts, 0, 0), Decl(exportDefaultNamespace.ts, 2, 1))
+>someProp : Symbol(someFunc.someProp, Decl(exportDefaultNamespace.ts, 2, 1))
+
diff --git a/tests/baselines/reference/exportDefaultNamespace.types b/tests/baselines/reference/exportDefaultNamespace.types
new file mode 100644
index 0000000000000..eebf33f51f4db
--- /dev/null
+++ b/tests/baselines/reference/exportDefaultNamespace.types
@@ -0,0 +1,15 @@
+=== tests/cases/conformance/declarationEmit/exportDefaultNamespace.ts ===
+export default function someFunc() {
+>someFunc : typeof someFunc
+
+    return 'hello!';
+>'hello!' : "hello!"
+}
+
+someFunc.someProp = 'yo';
+>someFunc.someProp = 'yo' : "yo"
+>someFunc.someProp : string
+>someFunc : typeof someFunc
+>someProp : string
+>'yo' : "yo"
+
diff --git a/tests/cases/conformance/declarationEmit/exportDefaultNamespace.ts b/tests/cases/conformance/declarationEmit/exportDefaultNamespace.ts
new file mode 100644
index 0000000000000..4724bda727ca3
--- /dev/null
+++ b/tests/cases/conformance/declarationEmit/exportDefaultNamespace.ts
@@ -0,0 +1,7 @@
+// @declaration: true
+
+export default function someFunc() {
+    return 'hello!';
+}
+
+someFunc.someProp = 'yo';