All human languages have restrictions on sound sequences, called phonotactic constraints. Knowledge of phonotactic constraints is typically tested using pseudoword rating tasks, e.g., an English speaker might be asked to rate acceptability or wordlikeness of the phonotactically illegal /bnɪk/ and the phonotactically legal /blɪk/. We introduce a new method of testing knowledge of phonotactic constraints. Instead of asking subjects to rate pseudowords, we ask them to assign pseudowords to pictures of novel objects. The set of available pseudowords is larger than the set of pictures and includes both legal and illegal pseudowords. We find legal pseudowords to be less likely to be left unassigned to pictures than illegal pseudowords. Thus, the listeners show knowledge of the phonotactics of English. We suggest that the present method has important advantages over rating tasks: it is a more direct measurement of the influence of phonotactics on the lexicon, and it allows the experimenter to detect influences of sound symbolism and lexical analogy and separate them from the influence of phonotactics.