pam_wheel.so doesn't work?

[Tim Hockin <thockin isunix it ilstu edu>]

I am trying to use the pam_wheel.so module with an application.  I want to
only allow members of a particular group in.  However, when I add this line
to the appropriate /etc/pam.d/ file, I get no change in behavior at all.
Whether a user is or is not a member of the group they are allowed.

auth       required     /lib/security/pam_wheel.so debug group=staff

I get nothing.  no debug messages, nothing.  If I misspell something on
that line, it logs an error, so I know this file is being examined..but
pam_wheel is not doing anything!  

Ideas?  

Tim