I'm writing a module to typeset problems/tests. Depending on a flag, solutions are either displayed or not. If the solutions are not displayed, I want to give a certain amount of empty vertical space for the student's work. This is where my difficulty begins. The typesetting works with the solutions displayed (\def\examshowsolutions} {yes}) but not with the empty vertical space (\def\examshowsolutions{no}). I get an "Emergency stop" that I cannot figure out. Here's the code for a minimal example of my difficulty.. \def\setupsolutions{ \doifelse{\examshowsolutions}{yes} {\defineenumeration[SOLUTION] % display the solutions [text=\Word{solution},number=no, after={\vskip1ex}]} {\definebuffer[SOLUTION] % hide solutions, \setupbuffer[SOLUTION][local=yes]} } \def\startsolution{\dosingleempty\dostartsolution} \def\dostartsolution[#1]{ \getparameters[solution][height=1em,] % set defaults (needed in case parameters missing) \iffirstargument \writestatus{DEBUG}{--First argument: |#1|} \getparameters[solution][#1,] \fi \writestatus{DEBUG}{--\solutionheight--} \startSOLUTION \writestatus{DEBUG}{--dostartsolution...finished} } \def\stopsolution{ \stopSOLUTION \writestatus{DEBUG}{--dostopsolution...1} \doif{\examshowsolutions}{no}{\godown[\solutionheight]} \writestatus{DEBUG}{--dostopsolution...finished} } \starttext \def\examshowsolutions{no} % control whether solutions are displayed \setupsolutions \startsolution % test without vertical height specified Here is a solution. \stopsolution \startsolution[height=5em] % test with vertical height specified Here is another solution. \stopsolution \stoptext The error occurs with the \startSOLUTION command. Here's the log file: (/home/kenny/texlive/2013/texmf-dist/tex/context/base/cont-yes.mkiv ConTeXt ver: 2013.05.28 00:36 MKIV current fmt: 2013.8.6 int: english/english system > 'cont-new.mkiv' loaded (/home/kenny/texlive/2013/texmf-dist/tex/context/base/cont-new.mkiv) system > files > jobname 'check', input './check', result 'check' fonts > latin modern fonts are not preloaded languages > language 'en' is active (/home/kenny/courses/Fall2014/phys1310/exam/check.tex{/home/kenny/texlive/2 013/texmf-dist/fonts/map/pdftex/context/mkiv-base.map} fonts > preloading latin modern fonts (second stage) fonts > typescripts > unknown library 'loc' {/home/kenny/texlive/2013/texmf-dist/fonts/map/dvips/lm/lm-math.map} {/home/kenny/texlive/2013/texmf-dist/fonts/map/dvips/lm/lm-rm.map} fonts > 'fallback modern rm 12pt' is loaded DEBUG > --1em-- )) ! Emergency stop. system > tex > error on line 0 in file : Emergency stop ... <empty file> <*> cont-yes.mkiv *** (job aborted, no legal \end found) ! ==> Fatal error occurred, no output PDF file produced!