CSS charset for mobile ?

Hello,
The MobileOK checker (used via Unicorn <http://qa-dev.w3.org/unicorn/>) 
asks to indicate the character encoding used 
<http://www.w3.org/TR/mobile-bp/#CHARACTER_ENCODING_USE>, even for CSS 
files. But it also asks to stick to CSS1 
<http://www.w3.org/TR/mobile-bp/#STYLE_SHEETS_USE>, which do not support 
@charset rules.
So, how am I supposed to do ? (I am not sure my ISP will let me change 
the HTTP header.)

-- 
Pierre Rudloff