diff --git a/layout/style/nsStyleSheetService.h b/layout/style/nsStyleSheetService.h
index 4342cd44e7c16a9c4bb9d30247316fa2f2f7830a..ee6bdf1ddc1428a5449a220c435a261ddd8b5927 100644
--- a/layout/style/nsStyleSheetService.h
+++ b/layout/style/nsStyleSheetService.h
@@ -47,6 +47,8 @@ class nsStyleSheetService final : public nsIStyleSheetService,
 
   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
 
+  void ZenMarkStylesAsChanged();
+
   static nsStyleSheetService* GetInstance();
   static nsStyleSheetService* gInstance;
 
