[NTG-context] readfile not understood

I do not understand while \readfile behaves differently from \input with regard to TeX-code processing. I have the following code: \readfile{metapost-setup} %(file with metapost inclusions) \starttext \startMPpage .. \stopMPpage \stoptext Replace the \readfile by: \input ../../../metapost-setup %(file with metapost inclusions) works ok. But with \readfile seems to be skipped silently, that is without any sign of it in the log. The convenience of \readfile should be, if I understand correctly, that it searches upwards to the root of directory tree. Which makes the series of ../'s unnecessary and allows for easily pushing the tex-files further down when their number grows. Can it be explained? Hans van der Meer