bin/40391: bogus error with usermod -g =uid

>Number:         40391
>Category:       bin
>Synopsis:       bogus error with usermod -g =uid
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 14 02:05:00 +0000 2009
>Originator:     reed@xxxxxxxxxxxxx
>Release:        NetBSD 5.0_BETA
>Organization:
  Jeremy C. Reed
>Environment:
        
        
Architecture: x86_64
Machine: amd64
>Description:
wrong error, wrong behaviour?

$ sudo usermod -g =uid adrion
usermod: Can't modify user `adrion': gid 0 is already in use

The error doesn't make sense.

>How-To-Repeat:
        
>Fix:
        

>Unformatted: