diff --git a/dom/indexedDB/test/browser_perwindow_privateBrowsing.js b/dom/indexedDB/test/browser_perwindow_privateBrowsing.js
index ef5426e6f2b0..e872a0650b1e 100644
--- a/dom/indexedDB/test/browser_perwindow_privateBrowsing.js
+++ b/dom/indexedDB/test/browser_perwindow_privateBrowsing.js
@@ -42,9 +42,9 @@ function test2()
   var win = OpenBrowserWindow({private: true});
   win.addEventListener("load", function onLoad() {
     win.removeEventListener("load", onLoad, false);
-    executeSoon(function() test3(win));
+    executeSoon(() => test3(win));
   }, false);
-  registerCleanupFunction(function() win.close());
+  registerCleanupFunction(() => win.close());
 }
 
 function test3(win)