diff --git a/images/autofs.proto b/images/autofs.proto
index c6013461e..2146ca89f 100644
--- a/images/autofs.proto
+++ b/images/autofs.proto
@@ -1,3 +1,5 @@
+syntax = "proto2";
+
 message autofs_entry {
 	required int32		fd			= 1;
 	required int32		pgrp			= 2;