diff --git a/kamailio/default.cfg b/kamailio/default.cfg
index f17230c..807ae09 100644
--- a/kamailio/default.cfg
+++ b/kamailio/default.cfg
@@ -556,6 +556,7 @@ route[EXTERNAL_TO_INTERNAL_RELAY]
 
     remove_hf_re("^X-.*");
     append_hf("X-AUTH-IP: $si\r\n");
+    append_hf("X-AUTH-PORT: $sp\r\n");
 
     t_on_reply("INTERNAL_REPLY");
     t_on_failure("INTERNAL_FAULT");