Abstract: A method and several embodiments of apparatus are disclosed for modulating the capacity of a gas compressor. A discharge valve member is formed with an opening therein and fluid communication between the compression chamber and a clearance pocket is selectively established by a slidable plunger element. In a first position, the plunger fills the opening in the discharge valve member to close fluid communication between the clearance pocket and the compression chamber. In a second position, the plunger element moves away from the valve member to establish fluid communication between the compression chamber and the clearance pocket, wherein the reexpansion volume is increased and the capacity of the compressor reduced. In the preferred embodiment, an apertured neck member is provided. The valve member is slidably guided by outer walls of the neck member, and the plunger has a stem designed to slidingly fit within the neck aperture.