Children's understanding of passives of certain mental state predicates appears to lag behind passives of so-called actional predicates, an asymmetry that has posed a major empirical challenge for theories of passive acquisition. This paper argues against the dominant view in the literature that treats the predicate-based asymmetry as theoretically irrelevant. We instead propose a novel account that locates the problem in the syntax of experiencer constructions. Synthesizing theoretical and developmental evidence, we build a case for an early misanalysis of transitive subject-experiencer constructions as unaccusatives -- structures that, by design, cannot passivize.