diff --git a/model/sync-state.h b/model/sync-state.h
index 03d4ec4..71e65c1 100644
--- a/model/sync-state.h
+++ b/model/sync-state.h
@@ -68,6 +68,8 @@
   LeafContainer m_leaves;
 };
 
+std::string & operator >> (std::string &DataBuffer, State &state);
+
 } // Sync
 
 #endif // SYNC_STATE_H