diff --git a/include/osmocom/bsc/signal.h b/include/osmocom/bsc/signal.h
index 9c0d5a3..1dde267 100644
--- a/include/osmocom/bsc/signal.h
+++ b/include/osmocom/bsc/signal.h
@@ -71,6 +71,7 @@
 	S_NM_STATECHG_OPER,	/* Operational State changed*/
 	S_NM_STATECHG_ADM,	/* Administrative State changed */
 	S_NM_OM2K_CONF_RES,	/* OM2K Configuration Result */
+	S_NM_OPSTART_ACK,	/* Received OPSTART ACK, arg is struct abis_om_fom_hdr* */
 };
 
 /* SS_LCHAN signals */