diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 0c666c0..1ccb136 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -204,6 +204,9 @@
 	for (i = 1; i < bsc->nat->mgcp_cfg->number_endpoints; ++i) {
 		if (bsc->nat->bsc_endpoints[i].bsc != bsc)
 			continue;
+		/* no one listening? a bug? */
+		if (!bsc->nat->bsc_endpoints[i].transaction_id)
+			continue;
 		if (strcmp(transaction_id, bsc->nat->bsc_endpoints[i].transaction_id) != 0)
 			continue;