diff --git a/openbsc/src/osmo-bsc_nat/bsc_ussd.c b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
index 2f68381..0ba6327 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_ussd.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
@@ -216,8 +216,7 @@
 {
 	struct msgb *msg;
 
-	conn->auth_timeout.data = conn;
-	conn->auth_timeout.cb = ussd_auth_cb;
+	osmo_timer_setup(&conn->auth_timeout, ussd_auth_cb, conn);
 	osmo_timer_schedule(&conn->auth_timeout, conn->nat->auth_timeout, 0);
 
 	msg = msgb_alloc_headroom(4096, 128, "auth message");