diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index 30f19f1..0584e70 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -1847,6 +1847,11 @@ vAPI.contextMenu.remove = function() {
     for ( var win of vAPI.tabs.getWindows() ) {
         this.unregister(win.document);
     }
+
+    this.menuItemId = null;
+    this.menuLabel = null;
+    this.contexts = null;
+    this.onCommand = null;
 };
 
 /******************************************************************************/