One challenge for the second language (L2) learner of English is to master a novel phonetic implementation of the voicing contrast, whereas another challenge is to learn how consonant sequences behave in connected speech. Learners of English coming from three different language backgrounds were tested; their native varieties were Bohemian Czech, Moravian Czech, and Slovak. The Moravian variety of Czech is more similar in voicing assimilation to the Slovak language than to the Bohemian variety of Czech. Percentage of phonetic voicing was measured in the L2 (i.e. English) word-final obstruents preceding three classes of sounds: voiceless and voiced obstruents, and sonorants. Bohemian and Moravian speakers exhibited different strategies in pre-sonorant contexts, following their native (variety-specific) assimilation rules.