Looking at

http://cvsweb.netbsd.org/bsdweb.cgi/src/usr.sbin/config/?sortby=date#dirlist

I see config changed 3 weeks ago, with comments

	Allow pseudo-devices to be declared with an interface attribute.
	For such pseud...

so, how old is the config program in userspace? 

When did you last update your real runtime environment to current?

-George