Listeners hearing distorted speech may be able to "correct" it if they have enough information about the nature of the distortion. We present evidence that this ability to correct a distorted speech signal is bought at a slight cost, namely, hyper-correction. We presented American English listeners with brief (85 msec) samples of 11 vowels that had been 1 kHz low-passed filtered. When presented in a way that gave them no chance to learn the filter characteristics they made 33.3% correct identifications. Many of the errors involved front vowels (those having a high Formant 2) being confused with back vowels (which often have F2 and F1 fused at 1 kHz or less). When the samples were preceded by a redundant precursor sentence filtered in the same way as the vowel samples, listeners raised their correct identifications to 50.1% but there was an increase in "hyper-correction" errors, i.e., where back vowels were identified as front vowels. This may provide clues as to how listeners "correct" distorted signals.