diff --git a/content/xul/document/src/nsXULPrototypeDocument.cpp b/content/xul/document/src/nsXULPrototypeDocument.cpp
index 6bc0815018c4..74abcc8ca668 100644
--- a/content/xul/document/src/nsXULPrototypeDocument.cpp
+++ b/content/xul/document/src/nsXULPrototypeDocument.cpp
@@ -766,6 +766,7 @@ nsXULPDGlobalObject::ClearGlobalObjectOwner()
             mScriptContexts[lang_ndx] = nsnull;
         }
     }
+    mGlobalObjectOwner = nsnull;
 }