diff --git a/content/xbl/src/nsXBLWindowHandler.cpp b/content/xbl/src/nsXBLWindowHandler.cpp
index 049b987c6f4..8f1d8fb90f6 100644
--- a/content/xbl/src/nsXBLWindowHandler.cpp
+++ b/content/xbl/src/nsXBLWindowHandler.cpp
@@ -82,8 +82,10 @@ nsXBLWindowHandler :: nsXBLWindowHandler (nsIDOMElement* aElement, nsIDOMEventRe
 nsXBLWindowHandler :: ~nsXBLWindowHandler ( )
 {
   --sRefCnt;
-  if ( !sRefCnt ) 
+  if ( !sRefCnt ) {
     delete sXBLSpecialDocInfo;
+    sXBLSpecialDocInfo = nsnull;
+  }
 }
 
 
diff --git a/layout/xbl/src/nsXBLWindowHandler.cpp b/layout/xbl/src/nsXBLWindowHandler.cpp
index 049b987c6f4..8f1d8fb90f6 100644
--- a/layout/xbl/src/nsXBLWindowHandler.cpp
+++ b/layout/xbl/src/nsXBLWindowHandler.cpp
@@ -82,8 +82,10 @@ nsXBLWindowHandler :: nsXBLWindowHandler (nsIDOMElement* aElement, nsIDOMEventRe
 nsXBLWindowHandler :: ~nsXBLWindowHandler ( )
 {
   --sRefCnt;
-  if ( !sRefCnt ) 
+  if ( !sRefCnt ) {
     delete sXBLSpecialDocInfo;
+    sXBLSpecialDocInfo = nsnull;
+  }
 }