This paper is a study of outside factors that may have a negative impact on a parser’s accuracy. The discussed phenomena can be divided into two classes, those related to treebank design, and those related to morphological tagging. Although the scope of the paper is limited to the Prague Dependency Treebank, two particular taggers and one particular parser, we believe that our observations may be of interest to future treebank designers. Anyway, since training parsers is usually not the only purpose of building treebanks, other good reasons may prevail and push aside the parser’s preferences. For that case, we suggest how the parser may use nasty input. More fine-grained elaboration of these workarounds and their evaluation is a matter of future work.