diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 922e15cd0119..c2a977079fba 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -7710,11 +7710,6 @@ var MousePosTracker = {
   _y: 0,
   _mostRecentEvent: null,
 
-  get _windowUtils() {
-    delete this._windowUtils;
-    return this._windowUtils = window.windowUtils;
-  },
-
   /**
    * Registers a listener, and then waits for the next refresh
    * driver tick before running the listener to see if the
@@ -7788,7 +7783,7 @@ var MousePosTracker = {
     let event = this._mostRecentEvent;
 
     if (event) {
-      let fullZoom = this._windowUtils.fullZoom;
+      let fullZoom = window.windowUtils.fullZoom;
       this._x = event.screenX / fullZoom - window.mozInnerScreenX;
       this._y = event.screenY / fullZoom - window.mozInnerScreenY;