"*The brightness of the background.
Set this to the symbol `dark' if your background color is dark, `light' if
your background is light, or nil (default) if you want Emacs to
-examine the brightness for you."
+examine the brightness for you. Don't set this variable with `setq';
+this won't have the expected effect."
:group 'faces
:set #'(lambda (var value)
(set-default var value)