A vapor compression system (200; 300; 400) has: a compressor (22); a first heat exchanger (30); a second heat exchanger (64); an ejector (38); separator (48); and an expansion device (70). A plurality of conduits are positioned to define a first flowpath sequentially through: the compressor; the first heat exchanger; the ejector from a motive flow inlet through (40) an outlet (44); and the separator, and then branching into: a first branch returning to the compressor; and a second branch passing through the expansion device and second heat exchanger to a secondary flow inlet (42). The plurality of conduits are positioned to define a bypass flowpath (202; 302; 402) bypassing the motive flow inlet and rejoining the first flowpath at essentially separator pressure but away from the separator.