diff --git a/externs/polymer-externs.js b/externs/polymer-externs.js
index fdbbd3620e..84651615d4 100644
--- a/externs/polymer-externs.js
+++ b/externs/polymer-externs.js
@@ -7,8 +7,8 @@
 
 /**
  * @typedef {{
+ * type: !Function,
  * value: *,
- * type: (!Function | undefined),
  * readOnly: (boolean | undefined),
  * computed: (string | undefined),
  * reflectToAttribute: (boolean | undefined),
@@ -23,18 +23,21 @@ let PolymerElementPropertiesMeta;
  */
 let PolymerElementProperties;
 
-/**
- * @typedef {{
- *   is: string,
- *   extends: (string | undefined),
- *   properties: (!PolymerElementProperties | undefined),
- *   observers: (!Array<string> | undefined),
- *   template: (!HTMLTemplateElement | string | undefined),
- *   hostAttributes: (!Object<string, *> | undefined),
- *   listeners: (!Object<string, string> | undefined)
- * }}
- */
-let PolymerInit;
+let PolymerInit = function(){};
+/** @type {string} */
+PolymerInit.prototype.is;
+/** @type {(string | undefined)} */
+PolymerInit.prototype.extends;
+/** @type {(!PolymerElementProperties | undefined)} */
+PolymerInit.prototype.properties;
+/** @type {(!Array<string> | undefined)} */
+PolymerInit.prototype.observers;
+/** @type {(!HTMLTemplateElement | string | undefined)} */
+PolymerInit.prototype.template;
+/** @type {(!Object<string, *> | undefined)} */
+PolymerInit.prototype.hostAttributes;
+/** @type {(!Object<string, string> | undefined)} */
+PolymerInit.prototype.listeners;
 
 let PolymerElementConstructor = function (){};
 /** @type {(string | undefined)} */
diff --git a/package.json b/package.json
index af32c6686c..ce532a1750 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
     "del": "^3.0.0",
     "dom5": "^2.3.0",
     "eslint-plugin-html": "^2.0.1",
-    "google-closure-compiler": "^20170626.0.0",
+    "google-closure-compiler": "^20170806.0.0",
     "gulp": "^3.9.1",
     "gulp-babel": "^6.1.2",
     "gulp-eslint": "^3.0.1",