> fixed in next beta
> 
> (you can replace gmatch by string.gmatch as a fast fix)

Thanks, that fixed the problem for one, but still it fails on my thesis with:

! LuaTeX error /usr/share/texmf/tex/context/base/back-exp.lua:868: attempt to index field '?' (a nil value).

<empty file>

I hope it is not because of my tex file.
Log attached.

Adam