diff --git a/include/osmocom/bsc/osmo_bsc_sigtran.h b/include/osmocom/bsc/osmo_bsc_sigtran.h
index df37cf44f..9cc2cfc71 100644
--- a/include/osmocom/bsc/osmo_bsc_sigtran.h
+++ b/include/osmocom/bsc/osmo_bsc_sigtran.h
@@ -26,7 +26,7 @@
 /* Allocate resources to make a new connection oriented sigtran connection
  * (not the connection ittself!) */
 enum bsc_con osmo_bsc_sigtran_new_conn(struct gsm_subscriber_connection *conn, struct bsc_msc_data *msc);
-struct gsm_subscriber_connection *bsc_conn_by_bsub(struct bsc_subscr *bsub);
+struct gsm_subscriber_connection *bsc_conn_by_bsub(const struct bsc_subscr *bsub);
 
 /* Open a new connection oriented sigtran connection */
 int osmo_bsc_sigtran_open_conn(struct gsm_subscriber_connection *conn, struct msgb *msg);
diff --git a/src/osmo-bsc/osmo_bsc_sigtran.c b/src/osmo-bsc/osmo_bsc_sigtran.c
index 04c2e9912..88ee01c2e 100644
--- a/src/osmo-bsc/osmo_bsc_sigtran.c
+++ b/src/osmo-bsc/osmo_bsc_sigtran.c
@@ -59,7 +59,7 @@ static struct gsm_subscriber_connection *get_bsc_conn_by_conn_id(int conn_id)
 	return NULL;
 }
 
-struct gsm_subscriber_connection *bsc_conn_by_bsub(struct bsc_subscr *bsub)
+struct gsm_subscriber_connection *bsc_conn_by_bsub(const struct bsc_subscr *bsub)
 {
 	struct gsm_subscriber_connection *conn;
 	if (!bsub)