diff --git a/src/main/protobuf/CommonMessages.proto b/src/main/protobuf/CommonMessages.proto
index dedfdbd..679d8b6 100644
--- a/src/main/protobuf/CommonMessages.proto
+++ b/src/main/protobuf/CommonMessages.proto
@@ -21,6 +21,7 @@ message HelloMessage {
 
 message CheckInMessage {
     repeated uint64 current_change_heads = 1;
+    uint64 current_change = 2;
 }
 
 enum Error {