Abstract: The present invention relates a control system and a method for controlling exhaust flow in an exhaust line of a combustion engine comprising at least one exhaust treatment component and an evaporator of a waste heat recovery system. The control system comprises a valve arrangement in the exhaust line control unit, a temperature sensor to sense a temperature of the exhaust treatment component and a control unit configured to position the valve arrangement in a first position, when the exhaust treatment component has a lower temperature than a specific temperature of exhaust gases directed flow through to the exhaust treatment component before being directed to flow through the evaporator, and in a second position, when the exhaust treatment component has a higher temperature than said specific temperature of exhaust gases that are directed to flow through the evaporator before being directed to flow through the exhaust treatment component.