diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index 494e8bb..e1ebc26 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -1258,7 +1258,9 @@
 		/* Now switch the flow over to a new port (BTS) */
 		port_old := flow[0].em.portnr;
 		flow[0].em.portnr := 10002;
+		f_rtpem_mode(RTPEM[0], RTPEM_MODE_RXONLY);
 		f_flow_modify(RTPEM[0], ep, call_id, "sendrecv", flow[0]);
+		f_rtpem_mode(RTPEM[0], RTPEM_MODE_BIDIR);
 
 		/* When handing over a call, the old source may still keep
 		 * transmitting for a while. We simulate this by injecting