[NTG-context] XeTeX w. ConTeXt question

Greetings, After a number of attempts (somewhat indistinguishable in my memory at this point) I've been able to run ConTeXt with XeTeX support (if that's the right nomenclature;). It works! But I do receive this error message: -- (/usr/local/TeTeX/share/texmf.tetex/tex/context/base/spec-tpd.tex systems : you should use pdfTeX binaries \wait= ) -- Looking in spec-tpd.tex, this error message comes from pdftexversion being undefined. Could someone clarify this for me? Kind regards