cups-1.4.6nb1 fails to build on stock NetBSD 5.1

[Georg Schwarz <georg.schwarz%freenet.de@localhost>]

Trying an unprivileged build of cups-1.4.6nb1 on a newly setup NetBSD 5.1 
system yields:

...
The following variables will affect the build process of this package,
cups-1.4.6nb1.  Their current value is shown below:

        * CUPS_GROUP = users
        * CUPS_GROUP = users
        * CUPS_SYSTEM_GROUPS = users
        * CUPS_SYSTEM_GROUPS = users
        * CUPS_USER = schwarz
        * CUPS_USER = schwarz

...
checking whether to use network default printers... yes
configure: error: The default system groups cannot contain the default CUPS 
group!
*** Error code 1

any idea what's going wrong?
The same issue exists on MacOS X, too.



-- 
Georg Schwarz  http://home.pages.de/~schwarz/
georg.schwarz%freenet.de@localhost +49 170 8768585