Recent studies of short-term phonetic interference suggest that code-switching can lead to momentary increases in L1 influence on L2. In an earlier study using a single acoustic measure (VOT), we found that Czech EFL learners’ pronunciation of English voiceless stops had shorter, i.e. more L1-Czech-like, VOTs in code-switched compared to L2-only sentences. The first aim of the current study was to test the prediction that native listeners would judge the code-switched English productions as more foreign-accented than the L2-only productions. The results provide only weak support for this prediction. The second aim was to test whether more native-like VOT values would correlate with improved accentedness scores. This was confirmed for sentence-initial stops.