An electrical connector includes a base having a number of passageways and a compartment in one end thereof. A cover is mounted to the base. The cover has a plurality of through holes corresponding to the passageways and a driving compartment corresponding to the compartment. The driving compartment has one single-step stopper. One recess is positioned adjacent the stopper and receives a stiffener therein for supporting the stopper. A cam is disposed in the driving compartment and the compartment to drive the cover moving relative to the base along a front-to-back direction.