diff --git a/src/libosmo-mgcp/mgcp_protocol.c b/src/libosmo-mgcp/mgcp_protocol.c
index 35141f8..555d6c6 100644
--- a/src/libosmo-mgcp/mgcp_protocol.c
+++ b/src/libosmo-mgcp/mgcp_protocol.c
@@ -323,7 +323,7 @@
 	}
 
 	/* Attach optional OSMUX parameters */
-	if (conn->osmux.state == OSMUX_STATE_NEGOTIATING) {
+	if (mgcp_conn_rtp_is_osmux(conn)) {
 		rc = msgb_printf(sdp, "X-Osmux: %u\r\n", conn->osmux.cid);
 		if (rc < 0)
 			goto error;