A turbine housing for a radial/mixed flow turbine, the turbine having a rotor comprising a plurality of blades disposed about a hub, the turbine housing comprising: a shroud configured to at least partially enshroud the rotor wherein a clearance is provided between the shroud and blade tips of the plurality of blades, the shroud and the hub defining a main passage of fluid flow in the turbine; and at least one injection opening provided in the shroud, the at least one injection opening configured to allow injection of a secondary flow of fluid into at least the clearance between the shroud and the blade tips.