diff --git a/src/sync-state.proto b/src/sync-state.proto
index 410726b..759b7d3 100644
--- a/src/sync-state.proto
+++ b/src/sync-state.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 message SyncState
 {
   required bytes name = 1;