An arrangement and method for heating an impact device (9) of a rock treating machine (Rtm) in low-temperature operating conditions. The arrangement comprises a warm-up mode (WM) for feeding pre-heated hydraulic fluid through a feed channel (19) to a hydraulic circuit (18) of the impact device. There are one or more hydraulic accumulators (Pa) in the hydraulic circuit. The feed channel is provided with a control element (CE) for limiting the feeding of the pre-heated hydraulic fluid during the warm-up mode. The control element limits the feeding of the pre-heated hydraulic fluid in the feed channel so that separating elements (Se) of the pressure accumulators do not move.