Example: \usemodule[nath] \starttext \startnathequation \underbrace{\mathstrut rr\dots r}_{n \text{times}} \stopnathequation \stoptext Error: ! Missing } inserted. <inserted text> } <to be read again> \o@dollar \o@math ->\o@dollar \relax \finishddelimbox@ ->\mathclose {} \o@math \egroup \delim@l #1#2->\mathopen {} \finishddelimbox@ \put@ {\the \ht \sizebox }\ht@... \mathph@nt ...tbox \nextbox \voidb@x {$\m@th #1{#2 }$} ... l.4 ...race{\mathstrut rr\dots r}_{n \text{times}} ? My guess is that the expansion of \mathstrut, being \vphantom(, is being misinterpreted as a delimiter (as '(' is active in nath), but that's just a layman's guess. nikolai -- ::: name: Nikolai Weibull :: aliases: pcp / lone-star / aka ::: ::: born: Chicago, IL USA :: loc atm: Gothenburg, Sweden ::: ::: page: www.pcppopper.org :: fun atm: gf,lps,ruby,lisp,war3 ::: main(){printf(&linux["\021%six\012\0"],(linux)["have"]+"fun"-97);}