Abstract: An electrical connector includes a housing stack having a first housing and a second housing stacked together with the first housing. The housing stack defines a mating end and a mounting end opposite the mating end. The housing stack defines signal contact cavities and ground contact cavities that extend continuously through the housings. At least one of the first housing and the second housing has pockets around the ground contact cavities with lossy spacers disposed therein each having a groove aligned with the corresponding ground contact cavity. Signal contacts are disposed in corresponding signal contact cavities. Ground contacts are disposed in corresponding ground contact cavities. The ground contacts are disposed in the grooves of the corresponding lossy spacers such that the ground contacts are coupled to the corresponding lossy spacers.