Postgresql gss user map doesn't work

Hello, I have a problem when I am using gss map. I want to map the user xxx(at)company(dot)com to db role company_com_xxxhere is my pa_hba.conf:=================# TYPE DATABASE USER ADDRESS METHODhost all all all gss include_realm=1 map=mymap
here is the pg_ident.conf=================# MAPNAME SYSTEM-USERNAME PG-USERNAMEmymap /(.*)@COMPANY.COM company_com_\1
However, it doesn't work, I got error message=================LOG: no match in usermap "mymap" for user "xxx" authenticated as "xxx(at)COMPANY(dot)COM"FATAL: GSSAPI authentication failed for user "xxx"DETAIL: Connection matched pg_hba.conf line 88: "host all all all gss include_realm=1 map=mymap"

but if I changed the map to =================# MAPNAME SYSTEM-USERNAME PG-USERNAMEmymap /(.*)@COMPANY.COM \1
then I can login, I have created role xxx and company_com_xxx in db side. even if I hard code the username in the mapping like=================# MAPNAME SYSTEM-USERNAME PG-USERNAMEmymap /(.*)@COMPANY.COM company_com_xxx
it still doesn't work. any idea?
Thanks in advance!
James