standalone attribute in XML declaration

Hi,

It took me ages to find out that the checker library fails with no
obvious reason if the XML declaration contains 'standalone="yes"', i.e.

        <?xml version="1.0" encoding="utf-8" standalone="yes"?>

just results in

        <tests outcome="PASS">
                <test name="MAIN_DOCUMENT" outcome="PASS"/>
        </tests>

whereas

        <?xml version="1.0" encoding="utf-8"?>

works fine.

Is this a desired behavior?

Cheers, Jens