A fluid flow machine has a main flow path, in which at least one row of blades (1) is arranged, and a shroud (2), which is embedded in a recess (3) of a component, with the component and the blades (1) being in relative rotational movement to each other. The assembly forming the shroud includes at least one internal chamber (7) which is suppliable with fluid from a source. The at least one internal chamber (7) is connected to the main flow path surrounding the blades (1) or to a cavity (9) surrounding the shroud (2) via at least one outlet (8) which is arranged on one side of the shroud (2). The shape of the outlet (8) and the shape of the outlet opening are such that a fluid barrier jet is generated at the outlet (8), which stops recirculation of fluid through the shroud cavity (9).