diff --git a/auth/v1/msg.proto b/auth/v1/msg.proto
index c14b773..cc778e7 100644
--- a/auth/v1/msg.proto
+++ b/auth/v1/msg.proto
@@ -43,6 +43,7 @@ message PermissionList {
 
 message UserSendOtpReq {
   string mobile = 1;
+  string referral_code = 2;
 }
 message UserSendOtpRes {
   int64 expired_at = 1;