diff --git a/libp2p/pubsub/pb/rpc.proto b/libp2p/pubsub/pb/rpc.proto
index f07da200..df38bad4 100644
--- a/libp2p/pubsub/pb/rpc.proto
+++ b/libp2p/pubsub/pb/rpc.proto
@@ -1,3 +1,5 @@
+// Modified from https://github.com/libp2p/go-libp2p-pubsub/blob/master/pb/rpc.proto
+
 syntax = "proto2";
 
 package pubsub.pb;