Weird behaviour on css aggregation

Hi
here some css from the Salamander theme, after and before aggregation; it seems like css aggregation doesn t read properly the ../ path

div#header .header-left {
-moz-background-clip:border;
-moz-background-inline-policy:continuous;
-moz-background-origin:padding;
background:transparent url(/sites/all/themes/images/salamander1/mast-l.png) no-repeat scroll 0 0;
padding:1px 0 14px;
}

div#header .header-left {
-moz-background-clip:border;
-moz-background-inline-policy:continuous;
-moz-background-origin:padding;
background:transparent url(../images/salamander1/mast-l.png) no-repeat scroll 0 0;
padding:1px 0 14px;
}