diff --git a/openbsc/src/bsc_init.c b/openbsc/src/bsc_init.c
index 815fe2b..bb1e382 100644
--- a/openbsc/src/bsc_init.c
+++ b/openbsc/src/bsc_init.c
@@ -443,7 +443,7 @@
 }
 
 /* Callback function for NACK on the OML NM */
-static int oml_msg_nack(int mt)
+static int oml_msg_nack(u_int8_t mt)
 {
 	if (mt == NM_MT_SET_BTS_ATTR_NACK) {
 		fprintf(stderr, "Failed to set BTS attributes. That is fatal. "
@@ -458,11 +458,14 @@
 static int nm_sig_cb(unsigned int subsys, unsigned int signal,
 		     void *handler_data, void *signal_data)
 {
+	u_int8_t *msg_type;
+
 	switch (signal) {
 	case S_NM_SW_ACTIV_REP:
 		return sw_activ_rep(signal_data);
 	case S_NM_NACK:
-		return oml_msg_nack((int)signal_data);
+		msg_type = signal_data;
+		return oml_msg_nack(*msg_type);
 	default:
 		break;
 	}