A method for controlling a valve arrangement in a vapour compression system, the vapour compression system comprising a compressor unit comprising one or more compressors, a heat rejecting heat exchanger, an ejector, a receiver, an expansion device and an evaporator arranged in a refrigerant path, wherein an outlet of the heat rejecting heat exchanger is connected to a primary inlet of the ejector, an outlet of the ejector is connected to the receiver, an outlet of the evaporator is connected to a secondary inlet of the ejector and to a first inlet of the valve arrangement, a gaseous outlet of the receiver is connected to a second inlet of the valve arrangement, and an outlet of the valve arrangement is connected to an inlet of the compressor unit, the valve arrangement thereby being arranged to supply refrigerant to the compressor unit from the gaseous outlet of the receiver and/or from the outlet of the evaporator, the method comprising the steps of: - defining a first mode of operation of the vapour compression system, in which the valve arrangement is operated to keep the first inlet of the valve arrangement closed and to keep the second inlet of the valve arrangement open, - defining a second mode of operation of the vapour compression system, in which the valve arrangement is operated to keep the first inlet of the valve arrangement open and to operate the second inlet of the valve arrangement to bypass vapour in order to maintain a pressure level in the receiver, - in the case that the vapour compression system is operated in the second mode of operation: - determining whether or not conditions for operating the vapour compression system in the first mode of operation are prevailing, and - in the case that conditions for operating the vapour compression system in the first mode of operating are prevailing, actively closing the first inlet of the valve arrangement and fully opening the second inlet of the valve arrangement, characterized in that the step of determining whether or not conditions for operating the vapour compression system in the first mode of operation are prevailing comprises the steps of: - determining a distribution of refrigerant supplied to the valve arrangement, including determining how large a portion of the refrigerant being supplied from the outlet of the valve arrangement to the compressor unit is received in the valve arrangement via the first inlet, and how large a portion is received via the second inlet, and - determining that conditions for operating the vapour compression system in the first mode of operation are prevailing if the portion of refrigerant received via the second inlet of the valve arrangement exceeds a predefined percentage of the refrigerant supplied from the outlet of the valve arrangement to the inlet of the compressor unit, said predefined percentage being at least 70%. - defining a first mode of operation of the vapour compression system, in which the valve arrangement is operated to keep the first inlet of the valve arrangement closed and to keep the second inlet of the valve arrangement open, - defining a second mode of operation of the vapour compression system, in which the valve arrangement is operated to keep the first inlet of the valve arrangement open and to operate the second inlet of the valve arrangement to bypass vapour in order to maintain a pressure level in the receiver, - in the case that the vapour compression system is operated in the second mode of operation: - determining whether or not conditions for operating the vapour compression system in the first mode of operation are prevailing, and - in the case that conditions for operating the vapour compression system in the first mode of operating are prevailing, actively closing the first inlet of the valve arrangement and fully opening the second inlet of the valve arrangement, - determining whether or not conditions for operating the vapour compression system in the first mode of operation are prevailing, and - in the case that conditions for operating the vapour compression system in the first mode of operating are prevailing, actively closing the first inlet of the valve arrangement and fully opening the second inlet of the valve arrangement, - determining a distribution of refrigerant supplied to the valve arrangement, including determining how large a portion of the refrigerant being supplied from the outlet of the valve arrangement to the compressor unit is received in the valve arrangement via the first inlet, and how large a portion is received via the second inlet, and - determining that conditions for operating the vapour compression system in the first mode of operation are prevailing if the portion of refrigerant received via the second inlet of the valve arrangement exceeds a predefined percentage of the refrigerant supplied from the outlet of the valve arrangement to the inlet of the compressor unit, said predefined percentage being at least 70%.