diff --git a/platform/firefox/frameModule.js b/platform/firefox/frameModule.js
index 7d8d147f0..1c54bfd55 100644
--- a/platform/firefox/frameModule.js
+++ b/platform/firefox/frameModule.js
@@ -205,7 +205,7 @@ var contentObserver = {
             openerURL: openerURL,
             parentFrameId: parentFrameId,
             rawtype: type,
-            tabId: -1,
+            tabId: '',
             url: location.spec
         };