A turbojet turbine or compressor stage is disclosed. The stage includes at least one rotor disk mounted inside a sectorized ring supported by a casing and including a circumferential flange radially clamped on an annular rail of the casing by a substantially C-shaped cross-section annular locking device which is axially engaged on the casing rail and on the flange of the ring. A substantially cylindrical heat shielding foil is interposed between the ring and the device. The foil or the device includes at least one extra thickness which respectively bears on the device, or the foil, to radially immobilize this foil.