Proper way to set flymake-errline in a theme

[Aaron Meurer]

Hi.

I've been trying to change the face flymake-errline in my theme, but
with little luck.  The default is a pink background, which doesn't
work so well (half the time the text is the same color or close the
same color as the background).  I want to make it underlined in red
and show up red.  So I added the following line to my theme file:

'(flymake-errline ((t (:foreground "red" :underline "red"))))

But with this, it still uses the pink background, in addition to this.
 I tried adding  :background nil to the above list, but that doesn't
work. Is there a way to reset the flymake-errline face to

I can add '(flymake-errline ((t nil))) to my .emacs, and it works, but
I'd rather keep all my face settings in the theme file.  How do I
reset the background to the default in the theme itself?

I can provide my full theme file and .emacs file if that would help.

Aaron Meurer