The invention relates to a bypass valve (1), in particular for an expansion machine (104) of a waste heat recovery system (100). The bypass valve (1) has a housing (2) with a valve chamber (9) formed therein. An inlet (3), an expander outlet (4) and a bypass outlet (5) are formed in the housing (2), which feed into the valve chamber (9). A closing element (6) is moveably arranged in the valve chamber (9). A valve seat (11) is formed on the housing (2). The closing element (6) cooperates with the valve seat (11) in order to open and close a first hydraulic connection from the inlet (3) to the expander outlet (4). A control valve (8) opens and closes a second hydraulic connection from the inlet (3) to the bypass outlet (5). The control valve (8) forms a first throttle point (21) in an open position. A second throttle point (22) is arranged between the valve chamber (9) and the bypass outlet (5). The control valve (8), the second throttle point (22) and the closing element (6) border a control chamber (9a). The first throttle point (21) has a greater flow cross-section than the second throttle point (22).