A pump for pumping fluid, wherein the pump comprises a pump head comprising a working chamber, a piston assembly configured for reciprocating within the working chamber to thereby displace fluid, a pump base accommodating a piston actuator being mechanically lockable to the piston assembly in a working mode of the pump to thereby transmit drive energy to the piston assembly to reciprocate, and a locking/unlocking mechanism configured to, upon unfastening the pump head from the pump base, mechanically unlock the piston actuator from the piston assembly in a maintenance mode of the pump.