Much research has explored the extent to which statistical computations account for the extraction of linguistic information. However, it remains to be studied how language-specific constraints are imposed over these computations. In the present study we investigated if the violation of a word-forming rule in Catalan (the presence of more than one mid vowel within a word) may interfere with word extraction by statistical computations. Catalan native adult participants were presented with a continuous speech stream composed of trisyllabic nonsense words that violated this linguistic constraint. In a subsequent test, participants did not recognize the words from matched foils. Nevertheless, the same words were recognized if the test comprised foils that never appeared during familiarization, or if both words and foils were presented visually. Results suggest that background linguistic knowledge modulates the recognition of statistically-coherent words, but not the on-line computations leading to their extraction. (Contains 1 figure and 1 table.)