diff --git a/common/protocol/Ola.proto b/common/protocol/Ola.proto
index 02896effa4..c9a97be1ff 100644
--- a/common/protocol/Ola.proto
+++ b/common/protocol/Ola.proto
@@ -18,6 +18,8 @@
  * Copyright (C) 2005 Simon Newton
  */
 
+syntax = "proto2";
+
 package ola.proto;
 
 option cc_generic_services = false;
diff --git a/common/rpc/Rpc.proto b/common/rpc/Rpc.proto
index 27eb002b28..9f9ec20dbb 100644
--- a/common/rpc/Rpc.proto
+++ b/common/rpc/Rpc.proto
@@ -18,6 +18,8 @@
  * Copyright (C) 2005 Simon Newton
  */
 
+syntax = "proto2";
+
 /*
  * Based on, but not guaranteed to be the same as the specification here:
  * http://protorpc.likbilen.com/Protorpcdocprotobuf.html