A fluid working machine of the type comprising working chambers of cyclically varying volume and low and high pressure valves to regulate the flow of working fluid into and out of the working chamber, from low and high pressure manifolds, in which the valves are electronically controlled on each cycle of working chamber volume, by way of valve actuation signals, to determine the net displacement of working chambers. Additional valve actuator signals are generated in response to determination that a valve or working chamber has been inactive to adapt the valve to operate more reliably when subsequently actuated, but without significantly altering the net displacement of working chambers.