diff --git a/content/xbl/src/nsBindingManager.h b/content/xbl/src/nsBindingManager.h
index af1245ff7f05..781d519b76b6 100644
--- a/content/xbl/src/nsBindingManager.h
+++ b/content/xbl/src/nsBindingManager.h
@@ -30,7 +30,7 @@ template<class E> class nsRefPtr;
 typedef nsTArray<nsRefPtr<nsXBLBinding> > nsBindingList;
 class nsIPrincipal;
 
-class nsBindingManager : public nsStubMutationObserver
+class nsBindingManager MOZ_FINAL : public nsStubMutationObserver
 {
 public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS