Listeners can use lexical knowledge to retune category boundaries of their native language to adapt to non-canonically produced phonemes. We asked whether phoneme boundaries in a second language are equally flexible, and whether perceptual learning transfers across languages. During a lexical decision task, German and Dutch listeners were exposed to "odd" pronunciation variants of a Dutch native speaker. Word-final [f] or [s] was replaced by an ambiguous sound. At test listeners categorized Dutch minimal word pairs ending in sounds along an [f]-[s] continuum. First as well as second language listeners (i.e., Dutch and German) showed boundary shifts of a similar magnitude. Moreover, following exposure to Dutch-accented English, Dutch listeners also showed effects of category retuning during test where they heard the same speaker speak her native language, Dutch. This suggests that first, lexical representations in a second language are specific enough to support lexically-guided retuning and second, that production patterns in a second language are deemed a stable speaker characteristic. Thus speaker-specific category retuning is used across languages.