“Jiao34/nian23/bek5” are all causative markers in Shanghai dialect, but the causative meanings they represent are different. This paper argues for a new classification of the markers’ causative types and discusses the grammaticalization of “bek5???”, whose meaning extends from ‘providing’ to passive. We analyze corpus data and hold that it is through negative causative factors (i.e. non-permission) that “bek5???” acquires its passive meaning. Only “bek5???” that denotes non-permission has both causative and passive interpretations. This semantic connection is crucial to why “bek5” can function both as a causative and a passive marker.