diff --git a/content/base/src/nsXMLHttpRequest.cpp b/content/base/src/nsXMLHttpRequest.cpp
index 8ce58571789..2ce4ab74309 100644
--- a/content/base/src/nsXMLHttpRequest.cpp
+++ b/content/base/src/nsXMLHttpRequest.cpp
@@ -1503,7 +1503,7 @@ nsXMLHttpRequest::GetInterface(const nsIID & aIID, void **aResult)
     *aResult = nsnull;
 
     nsresult rv;
-    nsCOMPtr<nsIWindowWatcher> ww(do_GetService("@mozilla.org/embedcomp/window-watcher;1", &rv));
+    nsCOMPtr<nsIWindowWatcher> ww(do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv));
     if (NS_FAILED(rv))
       return rv;