diff --git a/lib/utils/boot.js b/lib/utils/boot.js
index 701ee1e259..fdcefc5e64 100644
--- a/lib/utils/boot.js
+++ b/lib/utils/boot.js
@@ -11,4 +11,4 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
 window.JSCompiler_renameProperty = function(prop, obj) { return prop; }
 
 /** @namespace Polymer */
-let __PolymerBootstrap;
+