CSS3: border-radius set to 0 classified as bug

Hi,

I was quickly testing a layout[0] and tried to validate it. The CSS 
Validation found 12 bugs [1], which is mostly correct, since 11 of them 
are vendor specific styles, namely -moz and -webkit border-radius.

In line 95 of my stylesheet I wrote
	border-top-left-radius: 0;
in order to reset a previously set border radius.
The validator classifies this line as a bug, saying "0 is not a 
border-top-left-radius value :  0"

The W3C working draft says the following: "If either length is zero, the 
corner is square, not rounded." [2]

So as far as I understand "0" is a valid value for all radius 
properties. Therefore I'd see this as a bug in the validator.

Please correct me if I'm wrong.

Sincerely,
Norbert Wenzel

[0] http://www.norbertwenzel.at/test/OpacityBug/testpage.xhtml
[1] 
http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F%2Fwww.norbertwenzel.at%2Ftest%2FOpacityBug%2Ftestpage.xhtml&profile=css3&usermedium=all&warning=2&lang=en
[2] http://www.w3.org/TR/2002/WD-css3-border-20021107/#border-radius