An exhaust-gas turbocharger turbine of an internal combustion engine is provided with a spiral guide passage arranged in a turbine housing, a turbine impeller, a flow gap be ween the guide passage and the turbine impeller, and guide blades forming a guide cascade. The guide cascade with the guide blades projects axially from a support, arranged so as to be displaceable in the axial direction in the turbine housing, in such a way that the guide blades, in normal operation, are mounted in recesses of a housing wall part of the turbine housing, the recesses, in the form of a female piece, forming a mating profile shape for the guide blades. In braking operation of the internal combustion engine, the guide blades project into the flow gap during an axial displacement of the support. The device with actuation for the braking operation can be fitted as a complete module into the turbine spiral.