diff --git a/model/sync-state.h b/model/sync-state.h
index bfe2517..2806fdb 100644
--- a/model/sync-state.h
+++ b/model/sync-state.h
@@ -48,14 +48,14 @@
    * @param info name of the leaf
    * @param seq  sequence number of the leaf
    */
-  virtual void
+  virtual bool
   update (NameInfoConstPtr info, const SeqNo &seq) = 0;
 
   /**
    * @brief Remove leaf from the state tree
    * @param info name of the leaf
    */
-  virtual void
+  virtual bool
   remove (NameInfoConstPtr info) = 0;
 
   /**