diff --git a/mozilla/modules/plugin/base/src/ns4xPluginInstance.cpp b/mozilla/modules/plugin/base/src/ns4xPluginInstance.cpp
index ea26a579ace..d68c54ebf3a 100644
--- a/mozilla/modules/plugin/base/src/ns4xPluginInstance.cpp
+++ b/mozilla/modules/plugin/base/src/ns4xPluginInstance.cpp
@@ -957,7 +957,10 @@ ns4xPluginInstance::GetDOMWindow()
     return nsnull;
   }
 
-  return doc->GetWindow();
+  nsPIDOMWindow *window = doc->GetWindow();
+  NS_IF_ADDREF(window);
+
+  return window;
 }
 
 ////////////////////////////////////////////////////////////////////////