diff --git a/_locales/de/messages.json b/_locales/de/messages.json
index a923e39ca..0bf887bb5 100644
--- a/_locales/de/messages.json
+++ b/_locales/de/messages.json
@@ -33,7 +33,7 @@
   },
   "popupPowerSwitchInfo":{
     "message":"klicke das An-\/Ausschalter-Symbol, um µBlock für diese Webseite permanent ein- oder auszuschalten.\n\n<Strg>-Klick: schalte µBlock nur für diese spezifische Seite aus.",
-    "description":"English: Click: permanently disable\/enable µBlock for this site.\n\n<Ctrl>-click: disable µBlock only on this page."
+    "description":"English: Click: permanently disable\/enable µBlock for this site.\n\nCtrl+click: disable µBlock only on this page."
   },
   "popupBlockedRequestPrompt":{
     "message":"blockierte Anfragen",
diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index e2b20bb91..06f171c28 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -32,8 +32,8 @@
     "description":"appears as tab name in dashboard."
   },
   "popupPowerSwitchInfo":{
-    "message":"Click: permanently disable\/enable µBlock for this site.\n\n<Ctrl>-click: disable µBlock only on this page.",
-    "description":"English: Click: permanently disable\/enable µBlock for this site.\n\n<Ctrl>-click: disable µBlock only on this page."
+    "message":"Click: permanently disable\/enable µBlock for this site.\n\nCtrl+click: disable µBlock only on this page.",
+    "description":"English: Click: permanently disable\/enable µBlock for this site.\n\nCtrl+click: disable µBlock only on this page."
   },
   "popupBlockedRequestPrompt":{
     "message":"requests blocked",
diff --git a/_locales/fr/messages.json b/_locales/fr/messages.json
index 6e02048ed..2c1bc6423 100644
--- a/_locales/fr/messages.json
+++ b/_locales/fr/messages.json
@@ -32,8 +32,8 @@
     "description":"appears as tab name in dashboard."
   },
   "popupPowerSwitchInfo":{
-    "message":"Cliquez pour désactiver\/activer en permanence µBlock pour le site courant\n\n<Ctrl>-cliquez pour désactiver µBlock sur cette page seulement",
-    "description":"English: Click: permanently disable\/enable µBlock for this site.\n\n<Ctrl>-click: disable µBlock only on this page."
+    "message":"Cliquez pour désactiver\/activer en permanence µBlock pour le site courant\n\nCtrl+cliquez pour désactiver µBlock sur cette page seulement",
+    "description":"English: Click: permanently disable\/enable µBlock for this site.\n\nCtrl+click: disable µBlock only on this page."
   },
   "popupBlockedRequestPrompt":{
     "message":"Requêtes bloquées",
diff --git a/js/contentscript-end.js b/js/contentscript-end.js
index 41c7144c8..1c1ebaa16 100644
--- a/js/contentscript-end.js
+++ b/js/contentscript-end.js
@@ -584,7 +584,7 @@ var uBlockMessaging = (function(name){
             return;
         }
         var src = target[prop];
-        if ( !src ) {
+        if ( typeof src !== 'string' || src === '' ) {
             return;
         }
         // https://github.com/gorhill/uBlock/issues/174