A connector housing has a terminal accommodating chamber for a terminal and has an upper wall defining an opening part for insulator displacement. The connector housing has a flexible engagement piece at a front edge of the opening part. The connector housing has a first locking piece at a rear end thereof. A cover is assembled to the connector housing for closing the opening part. The cover has a second locking piece at a rear end thereof. The cover has an engagement projection at a front end thereof. When the cover is pushed down toward the opening part, the flexible engagement piece is locked with the engagement projection and the first locking piece is locked with the second locking piece.