[NTG-context] Forcing XeTeX output

Hi, is there a first-line comment directive or a \setupoutput[] parameter to force usage of XeTeX just like the --xtx commandline switch? Consider the following document: ---------------------- % ??? = xetex??? \starttext This is a piece of text \stoptext ---------------------- I just experimentally tried "engine=xetex", "tex=xetex" and "output=xetex" on the first line. The first two actually launch XeTeX, but they bail out with the comment "you should use pdfetex instad" and a \wait command, and the last one runs pdfetex instead and produces a DVI file. Philipp