Irrelevant getpwnam in radius

radiusd: GNU Radius version 1.3.1 (i686-pc-linux-gnu)
Compilation platform: linux
Debugging flags:
Compilation flags: PWD_SHADOW=SHADOW USE_SQL_POSTGRES USE_LOADABLE_MODULES
Compilation defaults:

On machine with radius and samba server installed, when all authentication
(including mlc) goes only through radius SQL-backend radius makes irrelevant
getpwnam-system calls.
[2007/02/13 12:14:54, 3] nsswitch/winbindd_user.c:winbindd_getpwnam(336)  [
0]: getpwnam matrix_kvartalo
Which in turn goes through winbind resolving then to ADS controller, so in
case of heavy loaded radius-server (67 req per sec) and slowly reporting
ADS-controller this behaviour seriasly affects radius performance. How can I
turn off _any_ local system checks in radius?

Typical users-profile:
DEFAULT         Auth-Type=Local,Password-Location=SQL
			NULL

Signed, Oleg Gawriloff.