diff --git a/openbsc/include/openbsc/bsc_api.h b/openbsc/include/openbsc/bsc_api.h
index 844e2aa..2062752 100644
--- a/openbsc/include/openbsc/bsc_api.h
+++ b/openbsc/include/openbsc/bsc_api.h
@@ -20,7 +20,7 @@
 			  uint8_t rr_cause, uint8_t chosen_channel,
 			  uint8_t encr_alg_id, uint8_t speech_mode);
 	void (*assign_fail)(struct gsm_subscriber_connection *conn,
-			 uint16_t rr_cause);
+			 uint8_t cause, uint8_t *rr_cause);
 	int (*clear_request)(struct gsm_subscriber_connection *conn,
 			      uint32_t cause);
 };
diff --git a/openbsc/src/bsc/osmo_bsc_api.c b/openbsc/src/bsc/osmo_bsc_api.c
index 537a9b4..f4b3148 100644
--- a/openbsc/src/bsc/osmo_bsc_api.c
+++ b/openbsc/src/bsc/osmo_bsc_api.c
@@ -45,7 +45,8 @@
 {
 }
 
-static void bsc_assign_fail(struct gsm_subscriber_connection *conn, uint32_t cause)
+static void bsc_assign_fail(struct gsm_subscriber_connection *conn,
+			    uint8_t cause, uint8_t *rr_cause)
 {
 }
 
diff --git a/openbsc/src/bsc_api.c b/openbsc/src/bsc_api.c
index 3abf4ba..c8ef4f4 100644
--- a/openbsc/src/bsc_api.c
+++ b/openbsc/src/bsc_api.c
@@ -203,7 +203,7 @@
 	struct bsc_api *api;
 	api = conn->bts->network->bsc_api;
 
-	api->assign_fail(conn, 0);
+	api->assign_fail(conn, 0, NULL);
 	return 0;
 }
 
@@ -263,10 +263,11 @@
 			break;
 		case GSM48_MT_RR_CHAN_MODE_MODIF_ACK:
 			rc = gsm48_rx_rr_modif_ack(msg);
-			if (rc < 0 && api->assign_fail)
+			if (rc < 0 && api->assign_fail) {
 				api->assign_fail(conn,
-						 GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE);
-			else if (rc >= 0 && api->assign_compl)
+						 GSM0808_CAUSE_NO_RADIO_RESOURCE_AVAILABLE,
+						 NULL);
+			} else if (rc >= 0 && api->assign_compl)
 				api->assign_compl(conn, 0,
 						  lchan_to_chosen_channel(conn->lchan),
 						  conn->lchan->encr.alg_id,