We investigated whether the interpretation of auditory stimuli as speech or non-speech affects audiovisual (AV) speech integration at the neural level. Perceptually ambiguous sine-wave replicas (SWS) of natural speech were presented to listeners who were either in "speech mode" or "non-speech mode". At the behavioral level, incongruent lipread information led to an illusory change of the sound only for listeners in speech mode. The neural correlates of this illusory change were examined in an audiovisual mismatch negativity (MMN) paradigm with SWS sounds. In an oddball sequence, "standards" consisted of SWS/onso/coupled with lipread/onso/, and "deviants" consisted of SWS/onso/coupled with lipread/omso/. The AV deviant induced a McGurk-MMN for listeners in speech mode, but not for listeners in non-speech mode. These results demonstrate that the illusory change in the sound by incongruent lipread information evoked an MMN which presumably takes place at a pre-attentive sensory processing stage. (Contains 3 figures.)