A connector has first and second housings (10A, 30A) that can be fit together along a fit-on direction. A female terminal (14) is mounted in a cavity (12) of a first housing (10A). A lance (19) is formed inside the first housing (10A) and locks the female terminal (14) in the cavity (12). The lance (19) can deform elastically in the flexibility allowance space (22) to unlock the female terminal (14). A retainer projection (34) is provided in a second housing (30A) and projects along a fit-in direction of the first and second housings (10A, 30A). The retainer projection (34) penetrates into the flexibility allowance space (22) as the first and second housings (10A, 30A) are fit together to prevent the lance (19) from flexing in an unlocking direction.