In Alemannic, there is remarkable morphological gap with verbal diminutives: They lack forms of the 1sg and, accordingly, the imperative. I try to identify the source of this gap that lies in prosodic wellformedness conditions for morphological words. Among the several potential causes that can lead to defective paradigms (Sims 2015: ch. 3), this phenomenon thus clearly belongs to the class that is related to the morphology-phonology interface.