--- a/browser/base/content/content.js
+++ b/browser/base/content/content.js
@@ -216,24 +216,24 @@ let AboutHomeListener = {
 
       case "settings":
         sendAsyncMessage("AboutHome:Settings");
         break;
     }
   },
 
   onPageHide: function(aEvent) {
-    if (event.target.defaultView.frameElement) {
+    if (aEvent.target.defaultView.frameElement) {
       return;
     }
     removeMessageListener("AboutHome:Update", this);
     removeEventListener("click", this, true);
     removeEventListener("pagehide", this, true);
-    if (event.target.documentElement) {
-      event.target.documentElement.removeAttribute("hasBrowserHandlers");
+    if (aEvent.target.documentElement) {
+      aEvent.target.documentElement.removeAttribute("hasBrowserHandlers");
     }
   },
 
   onSearch: function(aEvent) {
     sendAsyncMessage("AboutHome:Search", { searchData: aEvent.detail });
   },
 
   onFocusInput: function () {