diff --git a/pkg/polymer/test/js_interop_test.dart b/pkg/polymer/test/js_interop_test.dart
index e4bc6aa5307..154cd01d8a2 100644
--- a/pkg/polymer/test/js_interop_test.dart
+++ b/pkg/polymer/test/js_interop_test.dart
@@ -95,13 +95,22 @@ main() => initPolymer().run(() {
       // Text will update asynchronously
       expect(jsElem.shadowRoot.text, 'FOOBAR:40');
 
-      return new Future(() {
+      return _onTextChanged(jsElem.shadowRoot).then((_) {
         expect(jsElem.shadowRoot.text, 'FOOBAR:42');
       });
     });     
   });
 });
 
+Future<List<MutationRecord>> _onTextChanged(Node node) {
+  var completer = new Completer();
+  new MutationObserver((mutations, observer) {
+    observer.disconnect();
+    completer.complete(mutations);
+  })..observe(node, characterData: true, subtree: true);
+  return completer.future;
+}
+
 testInterop(jsElem) {
   expect(jsElem.shadowRoot.text, 'FOOBAR');
   var interop = new JsObject.fromBrowserObject(jsElem);