Wolfgang, From your observation I am inclined to guess that the \ifx falls prey to the collection of arguments. The \relax can be replaced by an extra pair {} behind the description: \answerblock{}{}% also typesets without the if-error. I more or less conclude that the lookahead from \dodoublegroupempty does not stop on the \if. If I remember correctly, that behaviour is to be expected from tex and the prospects for solving it generically within the format bleak. If Hans Hagen is listening, can he comment on this? Hans van der Meer On 26 mrt 2008, at 08:32, Wolfgang Schuster wrote:
Allthough Wolfgang's workaround saves the day, I feel this problem deserves solving inside ConTeXt, not outside it. Someday somewhere another person will stumble on the same problem -- a situation that can and should be avoided, in my view. Therefore I explain the problem here as fully as possible hoping someone knowledgeable with descriptions <<we might need to fall back to Taco or Hans>> will find the best remedy.
I would say the message comes from \dodoublegroupempty in \@@description.