The following code fails; however, it succeeds without newotf, and it succeeds with newotf if the defined font feature (*hebrew) is removed from the \definefont command. The characters that demonstrate the problem are HEBREW LETTER LAMED combined with HEBREW POINT HOLAM, followed by HEBREW LETTER ALEF (U05DC with combining U05B9 followed by U05D0). I have not come across other combinations that cause the problem, but I have not done an exhaustive search. \usemodule [newotf] \setupdirections [bidi=global] \definefontfeature [hebrew] [default] [lang=heb,ccmp=yes,script=hebr] \definefont [Hebrew] [sileot*hebrew] \starttext \startTEXpage This is okay:{\hfill\Hebrew לא} This is okay:{\hfill{\Hebrew לֹ}} This fails:{\hfill{\Hebrew לֹא}} \stopTEXpage \stoptext It reports: error: C:/ConTeXt/tex/texmf-context/tex/context/base/font-ots.lua:1586: attempt to index a number value tex error > tex error on line 13 in file C://Users/rik/Desktop/newotf-features.tex: ? <inserted text> \par <to be read again> \vss \pack_framed_do_bottom ...amedparameter \c!bottom \raggedbottomcommand <to be read again> \localendstrut \pack_framed_do_bottom \egroup \stopfittingpage ->\removeunwantedspaces \egroup \egroup \doif {\fittingpage... l.13 \stopTEXpage The same problem occurs in the same way with the following fonts, most of which are shipped with Windows: Arial Regular Arial Bold Arial Narrow David Regular David Bold Ezra SIL Regular Ezra SIL SR Regular Keter YG Medium Levenim MT Regular Levenim MT Bold Taamey David CLM Tahoma Regular Tahoma Bold Times New Roman Regular Times New Roman Bold