diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index 6f25b20..362af4e 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -361,7 +361,7 @@
 		var SDP_attribute_list attributes;
 
 		attributes := { valueof(ts_SDP_rtpmap(flow.pt, flow.codec)), valueof(ts_SDP_ptime(20)) };
-		if (isvalue(flow.fmtp)) {
+		if (isvalue(flow.fmtp) and flow.fmtp != "") {
 			attributes := attributes & { valueof(ts_SDP_fmtp(flow.pt, flow.fmtp)) };
 		}