Disagreement exists about how speakers monitor their internal speech. Production-based accounts assume that self-monitoring mechanisms exist within the production system, whereas comprehension-based accounts assume that monitoring is achieved through the speech comprehension system. Comprehension-based accounts predict perception-specific effects, like the perceptual uniqueness-point effect, in the monitoring of internal speech. We ran an extensive experiment testing this prediction using internal phoneme monitoring and picture naming tasks. Our results show an effect of the perceptual uniqueness point of a word in internal phoneme monitoring in the absence of such an effect in picture naming. These results support comprehension-based accounts of the monitoring of internal speech.