diff --git a/polymer/polymer-tests.ts b/polymer/polymer-tests.ts
index 70c5bce0a..a606692fd 100644
--- a/polymer/polymer-tests.ts
+++ b/polymer/polymer-tests.ts
@@ -44,7 +44,7 @@ function registerWebComponent(webComponentClass: Function, ...mixins: any[]): vo
 	for (var i in webComponent) {
 		// do not include polymer functions
 		if (i != "async" && i != "job" && i != "fire" && i != "asyncFire" && i != "cancelUnbindAll") {
-			var attribute: any = webComponent[i];
+			var attribute: any = (<any>webComponent)[i];
 			flattenedComponent[i] = attribute;
 		}
 	}