An inventive method of preventing unpowered reverse rotation in a compressor includes the steps of placing a solenoid valve at a location near compressor discharge. The valve is preferably actuated soon after the power to the motor is cut off, blocking the flow of refrigerant from expanding back toward the compression chambers of the compressor. The compressor is disclosed as a scroll compressor, but may also be a screw compressor. These two types of compressors are susceptible to undesirable unpowered reverse rotation when compressed refrigerant re-expands through the compression elements from the compressor discharge into the compressor suction. By blocking the flow of refrigerant, this unpowered reverse rotation is prevented. A high pressure switch can be positioned directly upstream of the solenoid valve to immediately stop the compressor if the valve malfunctions and blocks the flow of refrigerant during normal compressor operation. This high pressure switch will prevent the continued operation of the compressor with the blocked discharge line by sending a signal to a control to cut the power to the compressor motor. A pressure differential switch can be utilized in a similar manner to avoid undesirably high pressure differentials across the valve. Also, the valve itself may be equipped with the flow bypass that opens when pressure differential across the valve exceeds a safe limit.