A turbomachine has, on its inner casing (5) and on its shaft, recesses into which shrouds of rotor blades and/or of guide vanes (2a) protrude. The recesses are configured with wave-shaped contouring arrangements (10), which extend over their periphery. The contouring (10) extends over axially extending regions of the recess and consists of periodic elevations and depressions (14, 15) in the radial direction. They can also be effected on the radially extending regions of the recess and on the shrouds. The undulation-shaped contouring arrangements are used to counteract existing pressure fields and to reduce performance losses due to mixing processes between the leakage flow and the main flow.