An angular diffuser sector for a turbine engine compressor is provided. The sector includes an inner shroud; an outer shroud; a vane; a casing element mounted at least in part around one of the shrouds and having an open groove facing an axial end of the corresponding shroud; a wedge-forming fitting interposed between the casing element and the corresponding shroud, the wedge presenting a first surface that contacts with a bearing surface of the axial end of the corresponding shroud, and a second surface that is inclined relative to the first surface and that contacts with a corresponding sloping surface of the groove in the casing element; and a device that exerts an axial force on the wedge so as to keep its first surface in contact with the bearing surface and its second surface in contact with the sloping surface of the groove in the casing element.