Several intransitive verbs of motion or posture in Hiaki exhibit verb-stem suppletion conditioned by the number of the subject. There are also a few suppletive transitive verbs conditioned by the number of the object. We argue in this paper that suppletion in these verb roots is triggered only by underlying objects, and that the intransitive members of this class of verbs are unaccusative. To show this, we exploit the properties of the Hiaki applicative morpheme, which is productive with any agentive verb, transitive or intransitive, but may not occur with verbs with the general properties of unaccusative verbs. We show that the intransitive suppletive verbs may not co-occur with the applicative/benefactive morpheme -ria, despite the fact that several of them are apparently semantically/pragmatically appropriate as potential benefactive actions.