diff --git a/model/sync-diff-state.h b/model/sync-diff-state.h
index 7a889c4..6a43aef 100644
--- a/model/sync-diff-state.h
+++ b/model/sync-diff-state.h
@@ -86,10 +86,10 @@
   operator += (const DiffState &state);
   
   // from State
-  virtual void
+  virtual bool
   update (NameInfoConstPtr info, const SeqNo &seq);
 
-  virtual void
+  virtual bool
   remove (NameInfoConstPtr info);
   
 private: