Using of variables in media queries #28

Unless I've done something wrong latest build seemed to have a problem accepting:

@media screen and (orientation:portrait) and (max-width:$ipad_portrait_width){
body {
width : $ipad_portrait_width;
}
}

while it worked perfectly with:

@media screen and (orientation:portrait) and (max-width:768px){
body {
width : $ipad_portrait_width;
}
}

Of course, easy to come around for now, but maybe can make it as a fix in a future revision ?
thanks