config(8) out of sync with source

[William O'Higgins]

I've been googling this error:

Your version of config(8) is out of sync with your kernel source.

and looked through the FAQ, Handbook and list archives and I can't find
a fix.  I have installed this system via a 4.9 RELEASE CD, and updated
via cvsup a couple of times, and I need to recompile the kernel to turn
on some key features.  Is there a way to update config(8) so I can build
my new kernel?  Thanks.
-- 

yours,

William