One challenging problem that children overcome in learning new words is recognizing the hierarchical category of a label. For instance, one object could be called a Dalmatian, a dog, or an animal. Xu and Tenenbaum (2007) proposed a Bayesian model to explain how 3.5 to 5-year-olds solve this ambiguity. They emphasized children's appreciation for “suspicious coincidences:” a label applied to three identical toys is interpreted more narrowly than a label applied to one toy. Xu and Tenenbaum did not investigate children’s prior category knowledge, however. We replicated their “suspicious coincidence” effect and measured this knowledge. Unexpectedly, children with more category knowledge appreciated “suspicious coincidences” less. In a second experiment, repeatedly emphasizing novel labels caused all children to stop recognizing the “suspicious coincidence.” These data are inconsistent with the Bayesian account and suggest the phenomenon is influenced by subtler aspects of prior knowledge and by task-specific details.