This study explores whether knowledge of a L1 regressive voicing assimilation rule interferes with perception of word‐final voicing contrasts in an L2. Due to a regressive voicing assimilation rule, voicing in word‐final consonants is neutralized in both Hungarian and Polish. American English (AE) maintains a voicing contrast in this same context. In a perception task, 11 native Hungarian and 12 native Polish listeners identified AE word‐final consonants (e.g., [s]‐[z]) followed by voiced versus voiceless consonants. In a separate task, they identified the same consonants with the following consonantal context removed. The Hungarian and Polish listeners performed less accurately when the following context was present than when it was removed, suggesting that word‐final perception was influenced by the interference of the L1 rule.