XmlPullParser can't find attribute with a colon in its name

In my XML there's a tag with an attribute which has a name with a colon in it:

<GGS:bericht StUF:bestandsnaam="bestand.txt" >

I've tried all these combinations to try and return the value of this attribute:

parser.getAttributeValue(null, "StUF:bestandsnaam");
parser.getAttributeValue("StUF", "bestandsnaam");
parser.getAttributeValue(null, "bestandsnaam");
parser.getAttributeValue("bestandsnaam", "StUF");

... but they all return null.

If I manually remove the "StUF:" part of the attribute name, it works by calling:

parser.getAttributeValue(null, "bestandsnaam");

So how do you get the value of such an attribute? Without using the int-parameter version of getAttributeValue(), that is.