diff --git a/platform/firefox/vapi-client.js b/platform/firefox/vapi-client.js
index f5a761923..e810d79d8 100644
--- a/platform/firefox/vapi-client.js
+++ b/platform/firefox/vapi-client.js
@@ -29,7 +29,7 @@
 
 /******************************************************************************/
 
-(function() {
+(function(self) {
 
 // https://github.com/chrisaljoudi/uBlock/issues/464
 if ( document instanceof HTMLDocument === false ) {
@@ -542,6 +542,6 @@ vAPI.executionCost.stop('vapi-client.js');
 
 /******************************************************************************/
 
-})();
+})(this);
 
 /******************************************************************************/
diff --git a/platform/firefox/vapi-common.js b/platform/firefox/vapi-common.js
index 6fc7f5b85..6b0200d18 100644
--- a/platform/firefox/vapi-common.js
+++ b/platform/firefox/vapi-common.js
@@ -27,7 +27,7 @@
 
 /******************************************************************************/
 
-(function() {
+(function(self) {
 
 /******************************************************************************/
 
@@ -186,6 +186,6 @@ vAPI.localStorage.init('extensions.' + location.host + '.');
 
 /******************************************************************************/
 
-})();
+})(this);
 
 /******************************************************************************/