diff --git a/src/services/services.ts b/src/services/services.ts
index 04e63f6dbe1..fc9eb3e722d 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1687,7 +1687,7 @@ module ts {
                 if (displayName && displayName.length >= 2 && firstCharCode === displayName.charCodeAt(displayName.length - 1) &&
                     (firstCharCode === CharacterCodes.singleQuote || firstCharCode === CharacterCodes.doubleQuote)) {
                     // If the user entered name for the symbol was quoted, removing the quotes is not enough, as the name could be an
-                    // invalid identifer name. We need to check if whatever was inside the quotes is actually a valid identifier name.
+                    // invalid identifier name. We need to check if whatever was inside the quotes is actually a valid identifier name.
                     displayName = displayName.substring(1, displayName.length - 1);
                 }
                 
@@ -1708,6 +1708,13 @@ module ts {
             // Try to get a valid display name for this symbol, if we could not find one, then ignore it. 
             // We would like to only show things that can be added after a dot, so for instance numeric properties can
             // not be accessed with a dot (a.1 <- invalid)
+            var firstCharCode = symbol.name.charCodeAt(0);
+            if ((symbol.flags & SymbolFlags.Namespace) && (firstCharCode === CharacterCodes.singleQuote || firstCharCode === CharacterCodes.doubleQuote)) {
+                // If the symbol is external module, don't retry the completion list
+                // Also name of modules is invalid in completion list (i.e declare module "http" { var x; } | // <= request completion here, "http" should not be there)
+                return undefined;
+            }
+
             var displayName = getValidCompletionEntryDisplayName(symbol.getName(), program.getCompilerOptions().target);
             if (!displayName) {
                 return undefined;
diff --git a/tests/cases/fourslash/completionListWithAmbientDeclaration.ts b/tests/cases/fourslash/completionListWithAmbientDeclaration.ts
new file mode 100644
index 00000000000..f67ebfdf434
--- /dev/null
+++ b/tests/cases/fourslash/completionListWithAmbientDeclaration.ts
@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts"/>
+
+//// declare module "http" {
+////    var x;
+//// }
+//// /**/
+
+goTo.marker();
+debugger
+verifyNegatable.completionListContains("http");
\ No newline at end of file
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index f9476ee4d92..27caa0afe12 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -630,6 +630,7 @@ function verifyOperationIsCancelled(f) {
 var test = new FourSlashInterface.test_();
 var goTo = new FourSlashInterface.goTo();
 var verify = new FourSlashInterface.verify();
+var verifyNegatable = new FourSlashInterface.verifyNegatable(true);
 var edit = new FourSlashInterface.edit();
 var debug = new FourSlashInterface.debug();
 var format = new FourSlashInterface.format();