Listeners often perceive illusory vowels when presented with consonant sequences that violate phonotactic constraints in their language. Previous research suggests that the phenomenon motivates speech-perception models that incorporate surface phonotactic information and the acoustics of the speech tokens. In this article, inspired by Bayesian models of speech perception, we claim that the listener attempts to identify target phonemic representations during perception. This predicts that the phenomenon of perceptual illusions will be modulated not only by surface phonotactics and the acoustics of the speech tokens, but also by the phonological alternations of a language. We present the results of three experiments (an AX task, an ABX task and an identification task) with native Korean listeners, and native English listeners as a control group, showing that Korean listeners perceive different sets of illusory vowels in different phonological contexts, in accordance with the phonological processes of vowel deletion and palatalisation in the language.