CSS does not validate

The stylesheet in misc/drupal.css does not validate. The offending rule is

pre                       { white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -o-pre-wrap; white-space: -pre-wrap;}

According to the specification, this should be specified as follows:

'white-space' 

Value:  
normal | pre | nowrap | inherit 

Even if you feel is it tempting to use proprietaty values, you should not. Please correct.