In this paper we have identified six Romance patterns in which the presence of enclitic pronouns affects the stress assignment of the verb. We show that previous phonological analyses of these patterns that make reference to different incorporation sites within the prosodic hierarchy or post-lexical re-assignment of stress are incomplete and do not take into account the importance of the morphological make-up of the pronoun. Furthermore, we show that the order in which the clitics appear affects whether stress is shifted to the penultimate or final clitic in a cluster. We propose that these pronouns that trigger stress shift are morphologically distinct from clitics: they are weak pronouns in the sense of Cardinaletti & Starke 1999. As weak pronouns they can be stressed, they are morphologically more complex than clitics. Syntactically, they are lower than clitics and they land in a Spec position. All these properties explain the special stress patterns they trigger and in many cases the special ordering restrictions they have.