A connector is provided with a housing including a lock arm and a detector movable to a standby position and a detection position with respect to the housing. The detector includes a locking piece to be locked to the lock arm at the standby position before both housings are connected. At least one of the detector and the housing includes a locking strengthening portion for displacing the detector in a direction to increase a locking engagement of the locking piece and the lock arm in a part configured to slide in contact with the other when the detector moves from the standby position to the detection position.