In this squib we explore a strictly derivational explanation for the differences in possible middle voice constructions in Norwegian and Swedish. Whereas Norwegian allows by its lexical s-passive construction as well as a complex adjectival construction to stand in for middle semantics, only the latter option is available in Swedish. We argue that this contrast lies in the lexicalization of formal syntactico-semantic features and advance the claim that the failure to lexicalize all features in a derivational results in structures uninterpretable to the external interfaces (i.e., Exhaustive Lexicalization).