A centrifugal separator is configured for cleaning of crankcase gases from an internal combustion engine. The centrifugal separator includes a rotor rotatably arranged inside a stationary housing. The stationary housing includes an inlet for crankcase gases, a gas outlet, and a liquid outlet. The rotor includes a stack of separation discs, each separation disc of the stack of separation discs having a center axis, an inner surface, and an outer surface. A circumferential inner end surface extends between the inner surface and the outer surface. The circumferential inner end surface of at least one separation disc of the stack of separation discs includes a substantially flat first surface portion extending at an angle of at least 20 degrees to the center axis.