Does native knowledge introduce a perceptual bias against allophones that mismatch their context? In German, [x] only occurs after back vowels, while [ç] occurs elsewhere. German and English listeners heard “allophonic” ([ç-x]) and “non-allophonic” ([ç-f], [x-f]) continua after front and back vowels. Vowel affected German responses to [ç-x] and [ç-f], but not [x-f]. Vowel affected English responses to all continua. The asymmetric effect on German responses is explained as a perceptual expectation of [ç] after [y]. The effect on English responses is explained by acoustic misparsing, which causes some of the vowel's spectrum to cue a spectrally similar fricative.