An electrical connector includes a housing stack comprising a front housing and a rear housing coupled to the front housing at a seam. The housing stack defines plural contact cavities that extend continuously through the front housing and the rear housing between mating and mounting ends. A lossy spacer is disposed at the seam between the front and rear housings. The lossy spacer has plural contact cavities aligned with corresponding contact cavities of the housing stack. Signal and ground contacts are disposed in corresponding contact cavities of the housing stack. The signal contacts extend through the lossy spacer such that the signal contacts do not directly engage the lossy spacer. The ground contacts extend through the contact cavities in the lossy spacer such that the ground contacts are coupled by the lossy spacer.