A bypass valve (130) that regulates a flow of a fluid in a waste heat recovery system (100) is provided. The bypass valve (130) comprises a valve housing (220), an expander poppet (250) coupled to the valve housing (220) and adapted to prevent the flow of the fluid to an expander (140), and a valve stem (230) with at least a portion disposed in the valve housing (220) wherein the valve stem (230) is adapted to displace the expander poppet (250) to allow the fluid to flow to the expander (140), and regulate the flow of the fluid.