border-right causes a warning in the css validator

Hello all,

In order to reproduce this behaviour, please go to http://jigsaw.w3.org/css-validator/ . Now select the direct input box. Click on further options and set 'warnings' from 'normal' to 'all'. Next copy & paste the following into the box and evaluate:

p {

border-right: 1px solid black;

}

The css validator gives me a warning that border-right has been redefined. However if I
type in

p {

border-left: 1px solid black;

}

everything is fine. Moreover if I type in

p {

border-right-width: 1px;
border-right-style: solid;
border-right-color: black;
}

everything evaluates without any warnings as well.

Is this an error in the css validator or am I making a
mistake?

Regards
Christopher