diff --git a/test/unit/strict-template-policy.html b/test/unit/strict-template-policy.html
index bfb697dc32..5720829f7f 100644
--- a/test/unit/strict-template-policy.html
+++ b/test/unit/strict-template-policy.html
@@ -94,24 +94,22 @@
         // Safari errors are thrown on the top window, sometimes not, so
         // catch in both places
         let uncaughtError = null;
-        const onerror = window.onerror;
-        const topOnerror = window.top.topOnerror;
         window.onerror = window.top.onerror = function(err) {
           if (!uncaughtError) {
             uncaughtError = new Error(err);
           }
-        }
+        };
         assert.throws(function() {
           fn();
           // Re-throw any uncaughtErrors
           let err;
-          if (err = (uncaughtError || window.uncaughtError)) {
+          if ((err = (uncaughtError || window.uncaughtError))) {
             throw new Error(err.message);
           }
           // Force polyfill reactions and/or async template stamping
           Polymer.flush();
           // Re-throw any uncaughtErrors
-          if (err = (uncaughtError || window.uncaughtError)) {
+          if ((err = (uncaughtError || window.uncaughtError))) {
             throw new Error(err.message);
           }
         }, re);