A turbocharger (5) comprising a housing (10) including a compressor shroud (14) and a turbine shroud (12). The turbocharger (5) also includes a compressor wheel (18) and a turbine wheel (116, 216, 316, 416). The compressor wheel (18) includes a compressor hub (44) and a plurality of circumferentially spaced compressor blades (45, 46) extending radially from the compressor hub (44). The turbine wheel (116, 216, 316, 416) includes a turbine hub (124, 224, 324, 424) and a plurality of circumferentially spaced blades (126, 226, 326, 426) extending radially from the turbine hub (124, 224, 324, 424) with a hub surface (125, 225, 325, 425) extending between adjacent blades (126, 226, 326, 426). The turbine wheel (116, 216, 316, 416) also includes at least one surface discontinuity (135, 235, 335, 435) on the turbine hub surface (125, 225, 325, 425).