diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index 24bfdaf..deb9f3e 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -417,10 +417,13 @@
 			 * part that tells the MGW where we are listening for Osmux streams
 			 * that come from the MGW. We get a fully working connection in
 			 * one go. */
-			rx_hdl := c_OsmuxemDefaultRxHandle;
-			rx_hdl.cid := flow.osmux_cid;
-			f_osmuxem_register_rxhandle(pt, rx_hdl);
-			flow.osmux_cid_sent := true;
+			if (flow.osmux_cid != -1) {
+				/* We may still want to negotiate osmux CID later at MDCX */
+				rx_hdl := c_OsmuxemDefaultRxHandle;
+				rx_hdl.cid := flow.osmux_cid;
+				f_osmuxem_register_rxhandle(pt, rx_hdl);
+				flow.osmux_cid_sent := true;
+			}
 			cmd := ts_CRCX_osmux(get_next_trans_id(), ep, mode, call_id, flow.osmux_cid);
 			cmd.sdp := ts_SDP(flow.em.hostname, flow.em.hostname, "23", "42",
 					  flow.em.portnr, { int2str(flow.pt) }, attributes);