We examined if and when English-learning 17-month-olds would accommodate Japanese forms as labels for novel objects. In Experiment 1, infants (n = 22) who were habituated to Japanese word-object pairs looked longer at switched test pairs than familiar test pairs, suggesting that they had mapped Japanese word forms to objects. In Experiments 2 (n = 44) and 3 (n = 22), infants were presented with a spoken passage prior to habituation to assess whether experience with a different language would shift their perception of Japanese word forms. Here, infants did not demonstrate learning of Japanese word-object pairs. These findings offer insight into the flexibility of the developing perceptual system. That is, when there is no evidence to the contrary, 17-month-olds will accommodate forms that vary from their typical input but will efficiently constrain their perception when cued to the fact that they are not listening to their native language.