diff --git a/mozilla/layout/base/nsPresShell.cpp b/mozilla/layout/base/nsPresShell.cpp
index 2529fdf209b..2768a32cb14 100644
--- a/mozilla/layout/base/nsPresShell.cpp
+++ b/mozilla/layout/base/nsPresShell.cpp
@@ -1066,6 +1066,7 @@ protected:
   void DoReflow(nsIFrame* aFrame);
 #ifdef DEBUG
   void DoVerifyReflow();
+  void VerifyHasDirtyRootAncestor(nsIFrame* aFrame);
 #endif
 
   friend class nsPresShellEventCB;