The invention relates to an expansion valve for an air conditioning system, in particular for a refrigeration system that is operated with CO2 as the coolant. Said valve comprises a valve housing (22), which has a feed opening (23) and a drain opening (26), an expansion organ (24), which connects the feed opening (23) or a fluidic connection (17) that is linked to said opening to the drain opening (26) or a fluidic connection (18) that is linked to the latter. A bypass valve (27) lies parallel to the expansion organ (24). One end (41) of the valve housing (22) is equipped with a fixing section (42), which fixes the feed opening (23) and the drain opening (26) in a connection block (21) of the refrigeration system (11), said block containing the fluidic connections (17, 18).