diff --git a/mozilla/layout/base/src/nsPresContext.h b/mozilla/layout/base/src/nsPresContext.h
index 23a7c231946..992be396406 100644
--- a/mozilla/layout/base/src/nsPresContext.h
+++ b/mozilla/layout/base/src/nsPresContext.h
@@ -106,7 +106,7 @@ protected:
   void   GetUserPreferences();
 
 private:
-  friend PrefChangedCallback(const char*, void*);
+  friend int PrefChangedCallback(const char*, void*);
   void   PreferenceChanged(const char* aPrefName);
 };