In this paper, we offer an analysis of impersonal se (Impse) constructions in control infinitivals. We claim that se itself spells out the valued version of the [uD] feature that Holmberg (2010) and Roberts (2010) propose is a property of T in consistent null subject languages. As a corollary, we link Impse constructions to the consistent null subject status of a language (in the spirit of Belletti, 1982). Moreover, we claim that in Impse constructions there is a projected null external argument (prose) interpreted as non-referential because of the valued version of Holmberg's [uD] feature in T that se spells out. We also argue that ungrammatical sequences of Impse and other se result from the featural deficiency of prose; specifically, it lacks a specification for number.