The invention relates to strengthening the seal of a turbine casing by uncoupling the attachment flange from the rest of the housing. The casing comprises a body (12) which is externally reinforced by axial ribs (14) connected to an annular rib (25), and the attachment flange (19) is attached to said rib via an annular wall portion (27) which is thinner than the rib and the flange.
