diff --git a/src/libosmo-mgcp/mgcp_network.c b/src/libosmo-mgcp/mgcp_network.c
index 4144382..2da37b4 100644
--- a/src/libosmo-mgcp/mgcp_network.c
+++ b/src/libosmo-mgcp/mgcp_network.c
@@ -867,6 +867,15 @@
 	struct mgcp_endpoint *endp;
 	endp = conn->conn->endp;
 
+	/* Note: it is legal to create a connection but never setting a port
+	 * and IP-address for outgoing data. */
+	if (strcmp(inet_ntoa(conn->end.addr), "0.0.0.0") == 0 && conn->end.rtp_port == 0) {
+		LOGP(DRTP, LOGL_DEBUG,
+		     "endpoint:0x%x destination IP-address and rtp port is (not yet) known\n",
+		     ENDPOINT_NUMBER(endp));
+		return -1;
+	}
+
 	if (strcmp(inet_ntoa(conn->end.addr), "0.0.0.0") == 0) {
 		LOGP(DRTP, LOGL_ERROR,
 		     "endpoint:0x%x destination IP-address is invalid\n",