A valve system (30) for an engine arrangement. The valve system comprises a valve chamber (31) positioned at a junction of an inlet port (30b), an outlet port (30a) and a bypass port (30c), the inlet port (30b) configured for fluid communication with a flow of exhaust gas from an engine, the outlet port (30a) configured for fluid communication with an inlet (20a) of a turbine (20), and the bypass port (30c) configured for fluid communication with an exhaust aftertreatment device (24); a rotary valve comprising a valve rotor (39) which rotates about a valve axis within the valve chamber (31). The valve rotor (39) is rotatable about the valve axis between a first position in which the valve rotor permits gas flow through the bypass port (30c) and a second position in which the valve rotor blocks gas flow through the bypass port. At least one of the valve rotor and the valve chamber comprises a protrusion (148) and the other of the valve rotor and the valve chamber comprises a corresponding recess (150), wherein, in the first position, the protrusion and recess are spaced from one another, and, in the second position the recess receives the protrusion such that gas flow between the protrusion and recess is substantially prevented.