[NTG-context] Line under footer

[Holzminister]

Hi there!

I managed to draw a line under my footer (with the help of this
mailing list, of course ;) ), but how can I change its thickness?

This doesn't seem to work:
\setupbackgrounds[footer][text][frame=off, bottomframe=on, height=0pt,
depth=3pt]

Same effect with this one:
\setupbackgrounds[footer][text][frame=off, bottomframe=on, height=3pt]

Regards,
Eyke