In Istro-Romanian, there are two main groups of verbs, one inherited from Romance, one borrowed from the co-territorial Chakavian Croatian variety. The Croatian-derived verbs are specified for aspect, while the Romance ones are not. Generally, these groups do not interact. However, for a number of verbs previous scholars have claimed that they form suppletive aspectual pairs consisting of a prefixed Croatian-derived perfective verb and a simplex Romance imperfective. Given the anaspectual status of most Romance verbs such an analysis deserves scrutinous empirical verification. In this paper, we survey a comprehensive corpus of Istro-Romanian spanning from the second half of the 19th century to the 21st century with respect to seven alleged suppletive pairs. After describing their behaviour with respect to Vendlerian verb classes, as well as the semantics of their arguments, we come to the conclusion that we cannot speak of aspectual suppletion in the case of these seven verbs. Rather, some verbs are semantically specialized, so that they cannot conceivably form a pair. Where there is no obvious specialization, the prefixed Croatian verb focuses telicity, while the Romance one does not.