[NTG-context] Howto typeset physical half-life

Hi a year or so before one could simply typeset the physical half-life as shown in MWE: \usetypescript[palatino] \setupbodyfont[palatino] \starttext ½ α \m{T_α} \m{T_½} \stoptext The greek letter is just to show, that utf-8 works as expected. In actual beta (and probably longer before) this doesn't work anymore. What have I missed? Thanks Christian