The impersonal verb custar (lit. ‘cost’) in European Portuguese selects for a dative experiencer argument and an infinitival clause, which may be preceded by the preposition a. Interestingly, a reflexive clitic co-referential with the experiencer argument can be deleted (under conditions to be specified) if it is within the prepositional infinitival complement, but not within its prepositionless counterpart. We argue that the presence of the preposition a preceding the infinitival complement of custar correlates with obligatory control and show how deletion of reflexive clitics within the prepositional infinitivals can be captured under the movement theory of control ( MTC; see e.g. Hornstein 1991, 2001; Boeckx, Hornstein and Nunes 2010). More specifically, we show that if the infinitival subject is a deleted copy left by the “controller”, this copy can trigger deletion of the reflexive clitic as a way to satisfy a superficial ban on morphologically identical clitics in a local domain.