It has been argued that learning from errors contributes to competence development of teachers because it fosters the development of negative knowledge. This form of experiential knowledge focuses on wrong facts or actions which are inappropriate to solve certain problems. In our contribution, we present results from a prompting task study which investigated how negative knowledge develops in terms of its amount and quality along with growing professional expertise. N = 35 primary school teachers reflected upon how to act in 20 different critical classroom-situations. In the resulting verbal data, different forms of negative knowledge could be identified and compared quantitatively. Semi-experts showed the greatest amount and the most detailed negative knowledge. Novices had more detailed negative knowledge than experts. From these results, we conclude negative knowledge to result from error-making and reflection. Novices experience many errors, but may not have enough experience and practical knowledge to reflectively analyze them effectively. Semi-experts still are sometimes faced with error-experiences and remember their early errors; through their prolonged experience and reflection, they have developed extensive negative knowledge. Experts rely more strongly on their extensive repertoire of routines than on explicit knowledge. Thus, having negative knowledge is no longer important for them.