diff --git a/src/libosmo-mgcp-client/mgcp_client_fsm.c b/src/libosmo-mgcp-client/mgcp_client_fsm.c
index 7ff3a53..ab7af10 100644
--- a/src/libosmo-mgcp-client/mgcp_client_fsm.c
+++ b/src/libosmo-mgcp-client/mgcp_client_fsm.c
@@ -173,6 +173,11 @@
 
 	set_conn_mode(&mgcp_msg, &mgcp_ctx->conn_peer_local);
 
+	if (mgcp_ctx->conn_peer_local.x_osmo_osmux_use) {
+		mgcp_msg.x_osmo_osmux_cid = mgcp_ctx->conn_peer_local.x_osmo_osmux_cid;
+		mgcp_msg.presence |= MGCP_MSG_PRESENCE_X_OSMO_OSMUX_CID;
+	}
+
 	/* Note: We take the endpoint and the call_id from the remote
 	 * connection info, because we can be confident that the
 	 * information there is valid. For the local info, we explicitly
diff --git a/tests/mgcp_client/mgcp_client_test.c b/tests/mgcp_client/mgcp_client_test.c
index 432a09c..9c4392f 100644
--- a/tests/mgcp_client/mgcp_client_test.c
+++ b/tests/mgcp_client/mgcp_client_test.c
@@ -276,6 +276,17 @@
 	msg = mgcp_msg_gen(mgcp, &mgcp_msg);
 	printf("%s\n", (char *)msg->data);
 
+	printf("Generate X-Osmo-Osmux message (MDCX):\n");
+	msg = mgcp_msg_gen(mgcp, &mgcp_msg);
+	mgcp_msg.verb = MGCP_VERB_MDCX;
+	mgcp_msg.x_osmo_osmux_cid = 2;
+	mgcp_msg.presence =
+	    (MGCP_MSG_PRESENCE_ENDPOINT | MGCP_MSG_PRESENCE_CALL_ID |
+	     MGCP_MSG_PRESENCE_CONN_ID | MGCP_MSG_PRESENCE_CONN_MODE
+	     | MGCP_MSG_PRESENCE_X_OSMO_OSMUX_CID);
+	msg = mgcp_msg_gen(mgcp, &mgcp_msg);
+	printf("%s\n", (char *)msg->data);
+
 	printf("Overfolow test:\n");
 	mgcp_msg.verb = MGCP_VERB_MDCX;
 	mgcp_msg.presence =
diff --git a/tests/mgcp_client/mgcp_client_test.ok b/tests/mgcp_client/mgcp_client_test.ok
index 8fbe3ae..8b3e15b 100644
--- a/tests/mgcp_client/mgcp_client_test.ok
+++ b/tests/mgcp_client/mgcp_client_test.ok
@@ -100,6 +100,14 @@
 M: sendrecv
 X-Osmux: 2
 
+Generate X-Osmo-Osmux message (MDCX):
+MDCX 17 23@mgw MGCP 1.0
+C: 2f
+I: 11
+L: p:20, a:GSM, nt:IN
+M: sendrecv
+X-Osmux: 2
+
 Overfolow test: