A cover has a back wall facing the rear surface of a housing and a pair of facing walls projecting from the back wall and to be held on the housing. A lever is arranged rotatably along the outer surface of either one of the pair of facing walls. The pair of facing walls include, on outer surface sides, movement restricting portions arcuately extending in a rotating direction of the lever and capable of abutting on a surface of a detecting member on a detection position side before the housing and a mating housing are properly connected. The respective movement restricting portions on the outer surface sides of the both facing walls are point-symmetrically shaped with respect to a center position of the cover when the cover is viewed from behind.