The turbine arrangement includes a turbine including a turbine housing which defines a turbine cavity within which a turbine wheel is supported, an inlet upstream of the wheel and an outlet downstream. The arrangement also includes a flow passage configured to permit gas flow without interacting with the wheel, and a valve member moveable between an open configuration wherein gas may flow through the flow passage, and a closed configuration wherein gas is substantially prevented from flowing, a first actuator portion for moving the valve member between the configurations, and a second actuator portion in gas flow communication with a portion of the arrangement upstream of the wheel via an actuator gas passage. The arrangement is configured such that gas may flow through the actuator gas passage to the second actuator portion, where it acts on the second actuator portion to urge the valve member towards the closed configuration.