[NTG-context] units module has bug with markIV?

Hi all, "\Micro" in the "units" module failed, while "\Nano" and "\Milli" works fine. "$\mu$" works, so it doesn't look like a font problem. The following code works with pdftex/MarkII, but fails under Luatex 0.29beta/MarkIV. \usemodule[units] \starttext Hello world! $1\Micro\Meter$ $1\Micro\Second$ \stoptext Any hints? Thanks a lot! regards, shenchen