diff --git a/messageResponder.js b/messageResponder.js
index 65e91ea..7ed00c7 100644
--- a/messageResponder.js
+++ b/messageResponder.js
@@ -21,8 +21,6 @@
 
 (function(global)
 {
-  let ext = global.ext || require("ext_background");
-
   const {port} = require("messaging");
   const {Prefs} = require("prefs");
   const {Utils} = require("utils");
@@ -42,22 +40,6 @@
     SpecialSubscription
   } = require("subscriptionClasses");
 
-  // Some modules doesn't exist on Firefox. Moreover,
-  // require() throws an exception on Firefox in that case.
-  // However, try/catch causes the whole function to to be
-  // deoptimized on V8. So we wrap it into another function.
-  function tryRequire(module)
-  {
-    try
-    {
-      return require(module);
-    }
-    catch (e)
-    {
-      return null;
-    }
-  }
-
   function convertObject(keys, obj)
   {
     let result = {};
@@ -159,7 +141,7 @@
   {
     if (message.what == "issues")
     {
-      let subscriptionInit = tryRequire("subscriptionInit");
+      let subscriptionInit = require("subscriptionInit");
       let result = subscriptionInit ? subscriptionInit.reinitialized : false;
       return {filterlistsReinitialized: result};
     }
@@ -233,10 +215,11 @@
 
   port.on("filters.get", (message, sender) =>
   {
+    const {checkWhitelisted} = require("whitelisting");
+
     if (message.what == "elemhideemulation")
     {
       let filters = [];
-      const {checkWhitelisted} = require("whitelisting");
 
       let isWhitelisted = checkWhitelisted(sender.page, sender.frame,
         RegExpFilter.typeMap.DOCUMENT | RegExpFilter.typeMap.ELEMHIDE);