A stacked electrical connector formed by mating an upper and a lower housing having rows of cavities containing terminals is disclosed. The upper and lower housings have primary terminal assurance provided by lances integrally formed into the housings. A secondary terminal assurance system is provided to further secure the terminals within the housings. In one embodiment, secondary terminal assurance is to terminals in the upper housing by lower housing protrusions and to terminals in the lower housing by a hinge. In another embodiment, secondary terminal assurance is provided to terminals in the upper and lower housing by upper and lower protrusions of a lock plate.