Unknown SDP media, when faxing

Hi.

Asterisk 1.0.9

When receiving a fax, Asterisk tells me:
Aug 22 12:35:37 WARNING[2540]: chan_sip.c:2712 process_sdp: Unknown SDP media type in offer image 9286 udptl t38

Why? The fax is received, so all is ok, but the warning?

Tim Mickelson