--- a/parser/htmlparser/src/nsDTDUtils.h
+++ b/parser/htmlparser/src/nsDTDUtils.h
@@ -438,17 +438,17 @@ public:
                     nsISupports* aWebShell,
                     const PRUint32 aFlags);
 
   nsresult   AddObserver(nsIElementObserver* aObserver,eHTMLTags aTag);
   void       RemoveObserver(nsIElementObserver* aObserver);
   PRBool     Matches(const nsAString& aTopic);
 
 protected:
-  nsAutoString mTopic; // This will rarely be empty, so make it an auto string
+  nsString mTopic;
   nsVoidArray* mObservers[NS_HTML_TAG_MAX + 1];
   friend class nsMatchesTopic;
 };
 
 /*********************************************************************************************/
 
 
 struct TagList {