I have no idea what's going wrong ... When I uncomment the last line I'll get the following error. Latest minimal \setuparranging[doublesided] \setuppagenumbering [alternative=doublesided] \setupheads[alternative=margin,align=outer] \setupnumbering[alternative=doublesided] \starttext \chapter{Foo} \section{A long title} \input knuth \section{A long title} \input knuth \section{A long title} \input knuth \chapter{Bar} \startitemize \item one \item two \item three \stopitemize \section{A long title} \input knuth \section{A long title} \input knuth %\section{A long title} \input knuth \section{A long title} \input knuth \stoptext Herbert [ ... ] structure > sectioning > section @ level 3 : 0.2.4 -> A long title ! Extra \else. system > tex > error on line 14 in file 08-02-9.ctxcrop: Extra ... 4 \setupnumbering[alternative=doublesided] 5 6 \starttext 7 8 \chapter{Foo} 9 \section{A long title} \input knuth \section{A long title} \input knuth 10 \section{A long title} \input knuth 11 \chapter{Bar} 12 \startitemize \item one \item two \item three \stopitemize 13 \section{A long title} \input knuth \section{A long title} \input knuth 14 >> \section{A long title} \input knuth \section{A long title} \input knuth 15 16 \stoptext 17 18 19 20 21 %\definepapersize[card][width=792pt,height=612pt] 22 %\setuppapersize[card][card] 23 24 \dohandlestructurehead ...ureheadnumbertext \else \placestructureheadtext \f... l.14 ...title} \input knuth \section{A long title} \input knuth ?