When the parser encounters a url, it creates a ParsedValue that contains the url of the stylesheet and the property value. Later, when the url is converted, the stylesheet's url is used to resolve the relative url. The problem, though, is that when the binary css file is created, it sticks the path to the src file in as the stylesheet url. For example, "src/com/sun/javafx/scene/control/skin/caspian/caspian.css". What is needed is the stylesheet url as it is when the stylesheet is loaded. When the stylesheet is loaded, the stylesheet is given the file's URL. If the URLConverter can use the stylesheet URL instead of the parser sticking a URL in the ParsedValue, then all will be right with the world - or at least this tiny corner of it.

As a workaround, either use an absolute path for url's in the binary stylesheet, or set -Dbinary.css=false