diff --git a/apps/sdlan/src/sdlan_stun.erl b/apps/sdlan/src/sdlan_stun.erl
index c8abbc4..82a994a 100644
--- a/apps/sdlan/src/sdlan_stun.erl
+++ b/apps/sdlan/src/sdlan_stun.erl
@@ -107,7 +107,7 @@ handle_info({udp, Sock, Ip, Port, <<?PACKET_STUN_REQUEST:8, Body/binary>>}, Stat
             cookie = Cookie
         }),
         ok = gen_udp:send(Sock, Ip, Port, <<?PACKET_STUN_REPLY, StunReply/binary>>),
-        logger:debug("[sdlan_stun] stun_request network_id: ~p, client_id: ~p, hole: ~p, bytes: ~p", [NetworkId, ClientId, {Ip, Port}, <<?PACKET_STUN_REPLY, StunReply/binary>>])
+        logger:debug("[sdlan_stun] stun_request network_id: ~p, client_id: ~p, hole: ~p, bytes: ~p", [NetworkId, ClientId, {Ip, Port}, byte_size(<<?PACKET_STUN_REPLY, StunReply/binary>>)])
     end,
     {noreply, State};