diff --git a/test/unit/debounce.html b/test/unit/debounce.html
index 1c6e1520e5..f2fbc81935 100644
--- a/test/unit/debounce.html
+++ b/test/unit/debounce.html
@@ -216,16 +216,22 @@
       const timeoutCallback = sinon.spy(() => actualCallbacks.push(timeoutCallback));
       Polymer.enqueueDebouncer(Polymer.Debouncer.debounce(null, Polymer.Async.timeOut, timeoutCallback));
       // Set of short-running debouncers enqueued in the middle of first set
-      const nestedCallbacks = new Array(150).fill().map((_, i) => sinon.spy(() =>
-        actualCallbacks.push(nestedCallbacks[i])));
+      const nestedCallbacks = [];
+      for (let i=0; i<150; i++) {
+        nestedCallbacks.push(sinon.spy(() =>
+          actualCallbacks.push(nestedCallbacks[i])));
+      }
       // First set of short-running debouncers
-      const microtaskCallbacks = new Array(150).fill().map((_, i) => sinon.spy(() => {
-        actualCallbacks.push(microtaskCallbacks[i]);
-        if (i === 125) {
-          nestedCallbacks.forEach(cb => 
-            Polymer.enqueueDebouncer(Polymer.Debouncer.debounce(null, Polymer.Async.microTask, cb)));
-        }
-      }));
+      const microtaskCallbacks = [];
+      for (let i=0; i<150; i++) {
+        microtaskCallbacks.push(sinon.spy(() => {
+          actualCallbacks.push(microtaskCallbacks[i]);
+          if (i === 125) {
+            nestedCallbacks.forEach(cb => 
+              Polymer.enqueueDebouncer(Polymer.Debouncer.debounce(null, Polymer.Async.microTask, cb)));
+          }
+        }));
+      }
       microtaskCallbacks.forEach(cb => 
         Polymer.enqueueDebouncer(Polymer.Debouncer.debounce(null, Polymer.Async.microTask, cb)));
       // Expect short before long