Fluid flow adapter for a cylinder of a reciprocating compressor, the cylinder having a side wall provided with a valve seat, the fluid flow adapter comprising a filler element having an internal surface facing an internal volume of the cylinder and an external surface facing the valve, the filler element having at least a channel connecting the internal surface to the external surface, wherein the internal surface is flush with the side wall of the cylinder, the channel being configured to allow the passage of fluid between the internal volume of the cylinder and the valve.