diff --git a/include/osmocom/mgcp/mgcp_common.h b/include/osmocom/mgcp/mgcp_common.h
index 75d5a37..a1bbb19 100644
--- a/include/osmocom/mgcp/mgcp_common.h
+++ b/include/osmocom/mgcp/mgcp_common.h
@@ -50,6 +50,7 @@
 };
 
 #define MGCP_X_OSMO_IGN_HEADER "X-Osmo-IGN:"
+#define MGCP_X_OSMO_OSMUX_HEADER "X-Osmux:"
 
 /* Values should be bitwise-OR-able */
 enum mgcp_x_osmo_ign {
diff --git a/include/osmocom/mgcp_client/mgcp_client.h b/include/osmocom/mgcp_client/mgcp_client.h
index 9b57f10..be84356 100644
--- a/include/osmocom/mgcp_client/mgcp_client.h
+++ b/include/osmocom/mgcp_client/mgcp_client.h
@@ -95,6 +95,7 @@
 #define MGCP_MSG_PRESENCE_AUDIO_IP	0x0008
 #define MGCP_MSG_PRESENCE_AUDIO_PORT	0x0010
 #define MGCP_MSG_PRESENCE_CONN_MODE	0x0020
+#define MGCP_MSG_PRESENCE_X_OSMO_OSMUX_CID 0x4000
 #define MGCP_MSG_PRESENCE_X_OSMO_IGN	0x8000
 
 struct mgcp_msg {
@@ -113,6 +114,8 @@
 	struct ptmap ptmap[MGCP_MAX_CODECS];
 	unsigned int ptmap_len;
 	uint32_t x_osmo_ign;
+	bool x_osmo_osmux_use;
+	int x_osmo_osmux_cid; /* -1 is wildcard */
 	bool param_present;
 	struct mgcp_codec_param param;
 };
diff --git a/include/osmocom/mgcp_client/mgcp_client_fsm.h b/include/osmocom/mgcp_client/mgcp_client_fsm.h
index e170a25..c763d74 100644
--- a/include/osmocom/mgcp_client/mgcp_client_fsm.h
+++ b/include/osmocom/mgcp_client/mgcp_client_fsm.h
@@ -48,6 +48,11 @@
 	 * name than the BSC. An OsmoMGW will then ignore these and not fail on mismatches. */
 	uint32_t x_osmo_ign;
 
+	/*! send 'X-Osmux: %d' header (or "*" as wildcard). */
+	bool x_osmo_osmux_use;
+	/*! -1 means send wildcard. */
+	int x_osmo_osmux_cid;
+
 	/*! If left MGCP_CONN_NONE, use MGCP_CONN_RECV_ONLY or MGCP_CONN_RECV_SEND, depending on whether an audio RTP
 	 * address is set. If != MGCP_CONN_NONE, force this conn mode. */
 	enum mgcp_connection_mode conn_mode;