Meetme record

asterisk 1.6.2.24
WARNING[11350]: file.c:1165 ast_writefile: No such format ‘’

I have set MEETME_RECORDINGFORMAT=wav

dialplan:

exten => _X.,1,set(MEETME_RECORDINGFORMAT=wav);
exten => _X.,2,meetme(${EXTEN},1r);

why??