diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 50f1ce0d208..c28502907d7 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -380,7 +380,6 @@ namespace ts {
         }
 
         function mergeSymbol(target: Symbol, source: Symbol) {
-            //TODO: how to merge w/ shorthand ambient module?
             if (!(target.flags & getExcludedSymbolFlags(source.flags))) {
                 if (source.flags & SymbolFlags.ValueModule && target.flags & SymbolFlags.ValueModule && target.constEnumOnlyModule && !source.constEnumOnlyModule) {
                     // reset flag when merging instantiated module into value module that has only const enums
diff --git a/tests/baselines/reference/ambientShorthand_duplicate.js b/tests/baselines/reference/ambientShorthand_duplicate.js
new file mode 100644
index 00000000000..d99eb3d27dc
--- /dev/null
+++ b/tests/baselines/reference/ambientShorthand_duplicate.js
@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/ambient/ambientShorthand_duplicate.ts] ////
+
+//// [declarations1.d.ts]
+declare module "foo";
+
+//// [declarations2.d.ts]
+declare module "foo";
+
+//// [user.ts]
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo from "foo";
+
+
+//// [user.js]
+"use strict";
diff --git a/tests/baselines/reference/ambientShorthand_duplicate.symbols b/tests/baselines/reference/ambientShorthand_duplicate.symbols
new file mode 100644
index 00000000000..05856b47b92
--- /dev/null
+++ b/tests/baselines/reference/ambientShorthand_duplicate.symbols
@@ -0,0 +1,10 @@
+=== tests/cases/conformance/ambient/user.ts ===
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo from "foo";
+>foo : Symbol(foo, Decl(user.ts, 2, 6))
+
+=== tests/cases/conformance/ambient/declarations1.d.ts ===
+declare module "foo";
+No type information for this code.
+No type information for this code.
\ No newline at end of file
diff --git a/tests/baselines/reference/ambientShorthand_duplicate.types b/tests/baselines/reference/ambientShorthand_duplicate.types
new file mode 100644
index 00000000000..1520c5447ec
--- /dev/null
+++ b/tests/baselines/reference/ambientShorthand_duplicate.types
@@ -0,0 +1,10 @@
+=== tests/cases/conformance/ambient/user.ts ===
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo from "foo";
+>foo : any
+
+=== tests/cases/conformance/ambient/declarations1.d.ts ===
+declare module "foo";
+No type information for this code.
+No type information for this code.
\ No newline at end of file
diff --git a/tests/baselines/reference/ambientShorthand_merging.js b/tests/baselines/reference/ambientShorthand_merging.js
new file mode 100644
index 00000000000..f0aaefc6366
--- /dev/null
+++ b/tests/baselines/reference/ambientShorthand_merging.js
@@ -0,0 +1,18 @@
+//// [tests/cases/conformance/ambient/ambientShorthand_merging.ts] ////
+
+//// [declarations1.d.ts]
+declare module "foo";
+
+//// [declarations2.d.ts]
+declare module "foo" {
+    export const bar: number;
+}
+
+//// [user.ts]
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo, {bar} from "foo";
+
+
+//// [user.js]
+"use strict";
diff --git a/tests/baselines/reference/ambientShorthand_merging.symbols b/tests/baselines/reference/ambientShorthand_merging.symbols
new file mode 100644
index 00000000000..8a0ca5acb74
--- /dev/null
+++ b/tests/baselines/reference/ambientShorthand_merging.symbols
@@ -0,0 +1,11 @@
+=== tests/cases/conformance/ambient/user.ts ===
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo, {bar} from "foo";
+>foo : Symbol(foo, Decl(user.ts, 2, 6))
+>bar : Symbol(bar, Decl(user.ts, 2, 13))
+
+=== tests/cases/conformance/ambient/declarations1.d.ts ===
+declare module "foo";
+No type information for this code.
+No type information for this code.
\ No newline at end of file
diff --git a/tests/baselines/reference/ambientShorthand_merging.types b/tests/baselines/reference/ambientShorthand_merging.types
new file mode 100644
index 00000000000..78390a35dd8
--- /dev/null
+++ b/tests/baselines/reference/ambientShorthand_merging.types
@@ -0,0 +1,11 @@
+=== tests/cases/conformance/ambient/user.ts ===
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo, {bar} from "foo";
+>foo : any
+>bar : any
+
+=== tests/cases/conformance/ambient/declarations1.d.ts ===
+declare module "foo";
+No type information for this code.
+No type information for this code.
\ No newline at end of file
diff --git a/tests/cases/conformance/ambient/ambientShorthand_duplicate.ts b/tests/cases/conformance/ambient/ambientShorthand_duplicate.ts
new file mode 100644
index 00000000000..03a0dd72249
--- /dev/null
+++ b/tests/cases/conformance/ambient/ambientShorthand_duplicate.ts
@@ -0,0 +1,10 @@
+// @Filename: declarations1.d.ts
+declare module "foo";
+
+// @Filename: declarations2.d.ts
+declare module "foo";
+
+// @Filename: user.ts
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo from "foo";
diff --git a/tests/cases/conformance/ambient/ambientShorthand_merging.ts b/tests/cases/conformance/ambient/ambientShorthand_merging.ts
new file mode 100644
index 00000000000..a7bd7784d43
--- /dev/null
+++ b/tests/cases/conformance/ambient/ambientShorthand_merging.ts
@@ -0,0 +1,12 @@
+// @Filename: declarations1.d.ts
+declare module "foo";
+
+// @Filename: declarations2.d.ts
+declare module "foo" {
+    export const bar: number;
+}
+
+// @Filename: user.ts
+///<reference path="declarations1.d.ts" />
+///<reference path="declarations1.d.ts" />
+import foo, {bar} from "foo";