diff --git a/Jakefile.js b/Jakefile.js
index b13e2cfacf9..0c764758240 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -727,6 +727,7 @@ function runTestsAndWriteOutput(file) {
     var tapNotOk = /^not\sok/;
     var tapComment = /^#/;
     var typeError = /^\s+TypeError:/;
+    var debugError = /^\s+Error:\sDebug\sFailure\./;
     var progress = new ProgressBar("Running tests...");
     var expectedTestCount = 0;
     var testCount = 0;
@@ -734,6 +735,7 @@ function runTestsAndWriteOutput(file) {
     var successCount = 0;
     var comments = [];
     var typeErrorCount = 0;
+    var debugErrorCount = 0;
 
     ex.addListener("stdout", function (output) {
         var m = tapRange.exec(output);
@@ -757,6 +759,9 @@ function runTestsAndWriteOutput(file) {
             else if (typeError.test(output)) {
                 typeErrorCount++;
             }
+            else if (debugError.test(output)) {
+                debugErrorCount++;
+            }
             return;
         }
 
@@ -806,6 +811,10 @@ function runTestsAndWriteOutput(file) {
             console.log("# type errors: %s", typeErrorCount);
         }
 
+        if (debugErrorCount) {
+            console.log("# debug errors: %s", debugErrorCount);
+        }
+
         deleteTemporaryProjectOutput();
         if (beep) process.stdout.write("\u0007");
         fail("Process exited with code " + status);
diff --git a/src/compiler/transformers/module/es6.ts b/src/compiler/transformers/module/es6.ts
index 63b147b6e60..f513ac36dbb 100644
--- a/src/compiler/transformers/module/es6.ts
+++ b/src/compiler/transformers/module/es6.ts
@@ -4,9 +4,35 @@
 /*@internal*/
 namespace ts {
     export function transformES6Module(context: TransformationContext) {
+        const compilerOptions = context.getCompilerOptions();
+        const resolver = context.getEmitResolver();
+
+        let currentSourceFile: SourceFile;
+
         return transformSourceFile;
 
         function transformSourceFile(node: SourceFile) {
+            if (isExternalModule(node) || compilerOptions.isolatedModules) {
+                currentSourceFile = node;
+                return visitEachChild(node, visitor, context);
+            }
+            return node;
+        }
+
+        function visitor(node: Node) {
+            switch (node.kind) {
+                case SyntaxKind.ImportDeclaration:
+                    return visitImportDeclaration(<ImportDeclaration>node);
+            }
+
+            return node;
+        }
+
+        function visitImportDeclaration(node: ImportDeclaration) {
+            if (node.importClause && !resolver.isReferencedAliasDeclaration(node.importClause, /*checkChildren*/ true)) {
+                return undefined;
+            }
+
             return node;
         }
     }
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 18a95bc5ff0..aedd44fcb6a 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -3405,6 +3405,7 @@ namespace ts {
             || kind === SyntaxKind.TypeAliasDeclaration
             || kind === SyntaxKind.EnumDeclaration
             || kind === SyntaxKind.ModuleDeclaration
+            || kind === SyntaxKind.ImportDeclaration
             || kind === SyntaxKind.ImportEqualsDeclaration
             || kind === SyntaxKind.ExportDeclaration
             || kind === SyntaxKind.ExportAssignment;