An electrical connector assembly comprising: - an electrical connector having a carrier; - a mating connector having an actuating component; - a mate assist system adapted to assist the mating of the electrical connector and the mating connector, the mate assist system having a lever mounted to pivot on the carrier, wherein a rotating movement of the lever causes a mating movement of the electrical connector and the mating connector along a mating direction with respect to one another, the lever comprising parallel lengthwise arms along two lateral side walls of the carrier and a transverse actuating arm portion; - a locking system of the mate assist system, comprising locking elements on both lateral side walls of the carrier, and a flexible leg portion extending from each lengthwise arm of the lever, said flexible leg portion being lockably engaged with said locking element in a pre-locked position wherein rotation of the lever with respect to the carrier is prevented, and said flexible leg being able to cooperate with the actuating component upon mating together the electrical connector and the mating connector to release the flexible leg portion out of engagement with the locking element; wherein the pivotable lever is adapted to pivot with respect to the carrier at a pivot connection between the pre-locked and a locked position supporting the connection between the carrier and the mating connector; wherein the locking elements are a vertical rib protruding from each lateral side wall of the carrier, wherein each locking element comprises a locking knob and wherein the flexible leg is inserted in the pre-locked position of the lever between the lateral side wall of the carrier and the locking element, wherein the flexible leg extends in the pre-locked position of the lever along the rib substantially parallel to the flexible leg, wherein the locking leg extends, on the one hand, between the locking knob and the lateral side wall and on the other hand between the rib and another rib extending substantially along and parallel to the flexible leg. - an electrical connector having a carrier; - a mating connector having an actuating component; - a mate assist system adapted to assist the mating of the electrical connector and the mating connector, the mate assist system having a lever mounted to pivot on the carrier, wherein a rotating movement of the lever causes a mating movement of the electrical connector and the mating connector along a mating direction with respect to one another, the lever comprising parallel lengthwise arms along two lateral side walls of the carrier and a transverse actuating arm portion; - a locking system of the mate assist system, comprising locking elements on both lateral side walls of the carrier, and a flexible leg portion extending from each lengthwise arm of the lever, said flexible leg portion being lockably engaged with said locking element in a pre-locked position wherein rotation of the lever with respect to the carrier is prevented, and said flexible leg being able to cooperate with the actuating component upon mating together the electrical connector and the mating connector to release the flexible leg portion out of engagement with the locking element; wherein the pivotable lever is adapted to pivot with respect to the carrier at a pivot connection between the pre-locked and a locked position supporting the connection between the carrier and the mating connector; wherein the locking elements are a vertical rib protruding from each lateral side wall of the carrier, wherein each locking element comprises a locking knob and wherein the flexible leg is inserted in the pre-locked position of the lever between the lateral side wall of the carrier and the locking element, wherein the flexible leg extends in the pre-locked position of the lever along the rib substantially parallel to the flexible leg, wherein the locking leg extends, on the one hand, between the locking knob and the lateral side wall and on the other hand between the rib and another rib extending substantially along and parallel to the flexible leg.