Compressor Having Capacity Modulation

A compressor may include a shell assembly, a first scroll, a second scroll, a piston, and a piston-retention member. The piston engages the first scroll and may be partially received within a recess defined by the shell assembly. The piston and the shell assembly may cooperate to define a pressure chamber. The pressure chamber may be in selective fluid communication with a source of working fluid to control movement of the piston relative to the shell assembly. The piston-retention member may be mounted to the piston and selectively engage a rotationally fixed structure. The piston-retention member allows rotation of the piston relative to the first scroll in a first rotational direction and restricts rotation of the piston relative to the first scroll in a second rotational direction.