diff --git a/lib/utils/style-gather.html b/lib/utils/style-gather.html
index edbaa3cd75..c1ae6b7b23 100644
--- a/lib/utils/style-gather.html
+++ b/lib/utils/style-gather.html
@@ -22,6 +22,9 @@
     return Polymer.DomModule.import(moduleId);
   }
 
+  /** @typedef {{assetpath: string}} */
+  let templateWithAssetPath; // eslint-disable-line no-unused-vars
+
   /**
    * Module with utilities for collection CSS text from `<templates>`, external
    * stylesheets, and `dom-module`s.
@@ -70,7 +73,7 @@
         // include css from the first template in the module
         let t = m.querySelector('template');
         if (t) {
-          cssText += this.cssFromTemplate(t, m.assetpath);
+          cssText += this.cssFromTemplate(t, /** @type {templateWithAssetPath }*/(m).assetpath);
         }
         // module imports: <link rel="import" type="css">
         cssText += this.cssFromModuleImports(moduleId);