working state up to location update and classmark inquiry

diff --git a/src/gsm_04_08.c b/src/gsm_04_08.c
index 397f131..212b4ad 100644
--- a/src/gsm_04_08.c
+++ b/src/gsm_04_08.c
@@ -200,7 +200,7 @@
 static int mm_loc_upd_req(struct msgb *msg)
 {
 	struct gsm48_hdr *gh = msgb_l3(msg);
-	struct gsm_bts *bts = msg->bts_link->bts;
+	struct gsm_bts *bts = msg->trx->bts;
 	struct gsm48_loc_upd_req *lu;
 	struct gsm_subscriber *subscr;
 	u_int8_t mi_type;