diff --git a/src/sync-state.proto b/src/sync-state.proto
index 2aafb0c..26095e1 100644
--- a/src/sync-state.proto
+++ b/src/sync-state.proto
@@ -10,6 +10,7 @@
   required ActionType type = 2;
 
   optional uint64 seq = 3;
+  optional bytes locator = 4;
 }
 
 message SyncStateMsg