diff --git a/mvcc/mvccpb/kv.proto b/mvcc/mvccpb/kv.proto
index f0c82b57c..f150d26c7 100644
--- a/mvcc/mvccpb/kv.proto
+++ b/mvcc/mvccpb/kv.proto
@@ -43,4 +43,6 @@ message Event {
   // A DELETE/EXPIRE event contains the deleted key with
   // its modification revision set to the revision of deletion.
   KeyValue kv = 2;
+  // prev_kv holds the key-value pair before the event happens.
+  KeyValue prev_kv = 3;
 }