The Possible Word Constraint, or PWC, is a speech segmentation principle prohibiting to postulate word boundaries if a remaining segment contains only consonants. The PWC was initially formulated for English where all words contain a vowel and claimed to hold universally after being confirmed for various other languages. However, it is crucial to look at languages that allow for words without vowels. Two such languages have been tested: data from Slovak were compatible with the PWC, while data from Tarifiyt Berber did not support it. We hypothesize that the fixed word stress could influence the results in Slovak and report two word-spotting experiments on Russian, which has similar one-consonant words, but flexible word stress. The results contradict the PWC, so we suggest that it does not operate in the languages where words without vowels are possible, while the results from Slovak might be explained by its prosodic properties.