Plugin using is_member_of -- Do you see any problems?

[KW802]

Guys/gals, I have a plugin at "global_complete" to bounce banned members but I've gotten at least one report that a member who is not in the banned members group also got bounced.

Anybody see anything wrong with this chunk of code at "global_complete" that would cause somebody who does not belong to user group 8 to be also get bounced?

if (is_member_of($vbulletin->userinfo['userid'], 8)) 
{ 
     header('Location: {new site}'); 
     exit; 
}

Thanks,
Kevin