A spacer assembly for a rotor assembly of a gas turbine engine includes an endwall segment having a non-axisymmetric flowpath surface, a first depression and a second depression. A perimeter of the flowpath surface includes a forward edge, an aft edge, a suction side edge and a pressure side edge. The first depression is formed along the flowpath surface adjoining the suction side edge, and the second depression is formed along the flowpath surface adjoining the pressure side edge.