diff --git a/test/slotted.html b/test/slotted.html
index 51b5a12..211cfcb 100644
--- a/test/slotted.html
+++ b/test/slotted.html
@@ -32,7 +32,9 @@
       </iron-form>
     </template>
     <script>
+    HTMLImports.whenReady(function() {
       Polymer({is: 'slotted-form'});
+    });
     </script>
   </dom-module>