A compressor (10) may include first and second scrolls (68, 70), a seal assembly (20) and a valve ring (126). The first scroll (70) may include a first end plate (84) having a discharge passage(92), a modulation port (112), and a biasing passage (110). The modulation port (112) may be in communication with a first pocket (94) formed between spiral wraps (74, 86) of the first and second scrolls (68, 70). The biasing passage (110) may be in communication with a second pocket (96) formed between spiral wraps (74, 86) of the first and second scrolls (68, 70). The modulation valve ring (126) is axially displaceable relative to the seal assembly (20) and the first scroll (70) between first and second positions. The valve ring (126) may abut an end plate (84) of the first scroll (70) and close the modulation port (112) when in the first position. The valve ring (126) may abut an axially-facing surface of the seal assembly (20) and is spaced apart from the end plate (84) to open the modulation port (112) when in the second position.