--- a/browser/base/content/sanitize.js
+++ b/browser/base/content/sanitize.js
@@ -69,28 +69,26 @@ Sanitizer.prototype = {
     // Ensure open windows get cleared first, if they're in our list, so that they don't stick
     // around in the recently closed windows list, and so we can cancel the whole thing
     // if the user selects to keep a window open from a beforeunload prompt.
     let openWindowsIndex = itemsToClear.indexOf("openWindows");
     if (openWindowsIndex != -1) {
       itemsToClear.splice(openWindowsIndex, 1);
       let item = this.items.openWindows;
 
-      function onWindowsCleaned() {
+      let ok = item.clear(() => {
         try {
           let clearedPromise = this.sanitize(itemsToClear);
           clearedPromise.then(deferred.resolve, deferred.reject);
         } catch(e) {
           let error = "Sanitizer threw after closing windows: " + e;
           Cu.reportError(error);
           deferred.reject(error);
         }
-      }
-
-      let ok = item.clear(onWindowsCleaned.bind(this));
+      });
       // When cancelled, reject immediately
       if (!ok) {
         deferred.reject("Sanitizer canceled closing windows");
       }
 
       return deferred.promise;
     }