[css3-background] double '/' in border

I restarted working on css3-background in the CSS Validator, and ran into 
the issue of 'border-image'
'background' now forbid starting with a '/' which is good (thank you!), 
but border-image is defined as
"<'border-image-source'>||<'border-image-slice'>[/<'border-image-width'>?[/<'border-image-outset'>]?]?||<'border-image-repeat'>

meaning that you can have 'border-image-slice' / / 'border-image-outset'
This is the same issue as background starting with '/'.
Could it be fixed as well ?
Cheers,

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves