[NTG-context] reading attribute from ancestor element in XML

Hello list, I have an XML fragment like this: <div id="myid"> <p>¹² blah blah...</p> </div> In the typeset text I want to substitute the text of the sup element ("12") with the id ("myid") in its div grandfather. The xmlsetup associated to the sup element looks like this: \startxmlsetups xml:sup \xmlatt{\xmlfirst{#1}{../..}}{id} \stopxmlsetups This gives an error (TeX capacity exceeded). I'm using ConTeXt version 2015.06.15. I've tried \xmlfilter and \xmlall too, with different lpaths. Sometimes ConTeXt ends without errors, but I've never managed to get the text of that attribute. What's the right way to backtrack to parent and ancestor nodes?