diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index a6f5993f6c8..e00e9294529 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -1509,7 +1509,7 @@ namespace ts {
                     errorOnFirstToken(node, Diagnostics.export_modifier_cannot_be_applied_to_ambient_modules_and_module_augmentations_since_they_are_always_visible);
                 }
                 if (isExternalModuleAugmentation(node)) {
-                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.NamespaceModule, SymbolFlags.NamespaceModuleExcludes);
+                    declareModuleSymbol(node);
                 }
                 else {
                     let pattern: Pattern | undefined;
@@ -1531,12 +1531,8 @@ namespace ts {
                 }
             }
             else {
-                const state = getModuleInstanceState(node);
-                if (state === ModuleInstanceState.NonInstantiated) {
-                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.NamespaceModule, SymbolFlags.NamespaceModuleExcludes);
-                }
-                else {
-                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.ValueModule, SymbolFlags.ValueModuleExcludes);
+                const state = declareModuleSymbol(node);
+                if (state !== ModuleInstanceState.NonInstantiated) {
                     if (node.symbol.flags & (SymbolFlags.Function | SymbolFlags.Class | SymbolFlags.RegularEnum)) {
                         // if module was already merged with some function, class or non-const enum
                         // treat is a non-const-enum-only
@@ -1557,6 +1553,15 @@ namespace ts {
             }
         }
 
+        function declareModuleSymbol(node: ModuleDeclaration): ModuleInstanceState {
+            const state = getModuleInstanceState(node);
+            const instantiated = state !== ModuleInstanceState.NonInstantiated;
+            declareSymbolAndAddToSymbolTable(node,
+                instantiated ? SymbolFlags.ValueModule : SymbolFlags.NamespaceModule,
+                instantiated ? SymbolFlags.ValueModuleExcludes : SymbolFlags.NamespaceModuleExcludes);
+            return state;
+        }
+
         function bindFunctionOrConstructorType(node: SignatureDeclaration): void {
             // For a given function symbol "<...>(...) => T" we want to generate a symbol identical
             // to the one we would get for: { <...>(...): T }
diff --git a/tests/baselines/reference/augmentExportEquals7.errors.txt b/tests/baselines/reference/augmentExportEquals7.errors.txt
new file mode 100644
index 00000000000..1cb9ddc041c
--- /dev/null
+++ b/tests/baselines/reference/augmentExportEquals7.errors.txt
@@ -0,0 +1,22 @@
+/node_modules/@types/lib-extender/index.d.ts(2,16): error TS2300: Duplicate identifier '"lib"'.
+/node_modules/lib/index.d.ts(1,13): error TS2300: Duplicate identifier '"lib"'.
+/node_modules/lib/index.d.ts(2,19): error TS2300: Duplicate identifier '"lib"'.
+
+
+==== /node_modules/lib/index.d.ts (2 errors) ====
+    declare var lib: () => void;
+                ~~~
+!!! error TS2300: Duplicate identifier '"lib"'.
+    declare namespace lib {}
+                      ~~~
+!!! error TS2300: Duplicate identifier '"lib"'.
+    export = lib;
+    
+==== /node_modules/@types/lib-extender/index.d.ts (1 errors) ====
+    import * as lib from "lib";
+    declare module "lib" {
+                   ~~~~~
+!!! error TS2300: Duplicate identifier '"lib"'.
+        export function fn(): void;
+    }
+    
\ No newline at end of file
diff --git a/tests/cases/compiler/augmentExportEquals7.ts b/tests/cases/compiler/augmentExportEquals7.ts
new file mode 100644
index 00000000000..c287bcbe8c4
--- /dev/null
+++ b/tests/cases/compiler/augmentExportEquals7.ts
@@ -0,0 +1,10 @@
+// @Filename: /node_modules/lib/index.d.ts
+declare var lib: () => void;
+declare namespace lib {}
+export = lib;
+
+// @Filename: /node_modules/@types/lib-extender/index.d.ts
+import * as lib from "lib";
+declare module "lib" {
+    export function fn(): void;
+}