In this paper, we investigate the German s(ich)l(assen)-middle—a construction semantically similar to dispositional middles, but crucially different in its syntactic properties. We provide a syntactic analysis of sl-middles that accounts for all these differences: sl-middles involve a reflexively marked anticausative (sich lassen) that embeds a morphologically unmarked passive (which we call passive infinitive due to the infinitival marking on the verb). Dispositionality in this construction is argued to derive from the lexico-semantic properties of the matrix predicate lassen, providing support for the claim that the middle is a notional, rather than a grammatical category. Furthermore, under our analysis sl-middles have crucial implications for the theory of passivization as well as Binding Theory. First, morphological marking is not a constitutive feature of passives (contra Haspelmath 1990). The absence of passive morphology in sl-middles is explained by the reduced size of the complement. Second, our approach entails that the grammatical subject originates as the logical object of the embedded predicate, and is thus structurally lower than the non-thematic reflexive pronoun which it binds. Sl-middles are hence a further instance of such a peculiar binding configuration, lending independent support to Schäfer's (2008) analysis of anticausatives and middles.