Using MATE with MGCP

I have wireshark version 1.12.8 and am trying to use MATE to analyse MGCP capture.

Using the following mate file:

Pdu mgcp_pdu Proto mgcp Transport ip {
    Extract addr From ip.addr;
    Extract transid From mgcp.transid;
    Extract endpoint From mgcp.req.endpoint;
    Extract callid From mgcp.param.callid;
};
Done;

Starting wireshark with option to load mate file.

wireshark -o "mate.config: mgcp.mate" -r mcgp.cap

After loading files wireshark show the MATE heading in the Packet Details frame but only with source and destination ip addresses. None of MGCP parameters are displayed. Is this a bug or am I doing something wrong?

Thanks,

Paul