This study investigates a non-standard use of causative morphology in Turkish which we label 'involvee causative' (InvC). InvCs differ from regular causatives in that their subject argument is not interpreted as causing or bringing about the event described by the verb but as merely being involved in this event. Moreover, unlike regular causatives, InvCs are unable to take agent-oriented adverbs and instrument phrases and to passivize. In previous research, failure of these diagnostics has been taken as evidence for an unaccusative structure. However, we present evidence that this cannot hold for InvCs, which must be analyzed as containing a thematic Voice head introducing an external argument. This argument is interpreted not as an agent but as an involvee which possesses only a subset of proto-agent properties. We conclude that agent-oriented adverbs, instrument phrases and passivization are not proper unaccusativity diagnostics, as often assumed, but are sensitive to the interpretation of the external argument, requiring, at least in Turkish, an argument with fully agentive semantics.