Index: lib/stats.js
===================================================================
--- a/lib/stats.js
+++ b/lib/stats.js
@@ -35,12 +35,9 @@
   return blockedPerPage.get(page) || 0;
 };
 
-FilterNotifier.addListener(function(action, item, newValue, oldValue, page)
+FilterNotifier.on("filter.hitCount", (filter, newValue, oldValue, page) =>
 {
-  if (action != "filter.hitCount" || !page)
-    return;
-
-  if (!(item instanceof BlockingFilter))
+  if (!(filter instanceof BlockingFilter) || !page)
     return;
 
   Prefs.blocked_total++;
@@ -58,7 +55,7 @@
   }
 });
 
-Prefs.on("show_statsinicon", function()
+Prefs.on("show_statsinicon", () =>
 {
   ext.pages.query({}, function(pages)
   {