[NTG-context] How to enable tabular numerals with simplefonts and otf?

Hi, How can I enable tabular numerals please? Test file, that does not work: --8<---------------cut here---------------start------------->8--- \usemodule[simplefonts] \setmainfont[LinLibertineIO][size=10pt, tnum=yes] \starttext \addff{tnum} \setff{tnum} 565656565656X\par 000000000000X \stoptext --8<---------------cut here---------------end--------------->8--- TIA for any help! -- Peter