This study investigated whether learners with a phonemic vowel quantity distinction (VQD) in their L1 have an advantage when acquiring allophonic vowel length in L2. Many languages contain a phonological rule to devoice final consonants. While English maintains a phonemic contrast between voiced and voiceless syllable codas ("bat" vs. "bad," e.g.), it accompanies an allophonic contrast in the duration of the preceding vowel, resulting in longer vowels before voiced codas than before voiceless ones. German-L1 English learners (group 1), whose L1 has devoiced codas and VQD, and Russian-L1 English learners (group 2), whose L1 also devoices codas but has no VQD, performed a vowel production and XAB vowel perception task, designed to determine whether group 1 perceived and produced longer vowels before English voiced stop codas, compared to group 2. Both perceived but did not produce vowel lengthening before English voiced codas, which was significantly different from native English speakers.