The invention refers to a method for controlling sleep operation of a radio network node (12) that supports multiple sleep modes, the method comprising determining (110) which one or more of the supported sleep modes, if any, would prevent the radio network node (12) from being able to meet requirements on a quality of service, such as a maximum allowable data latency, to be provided by the radio network node (12); and preventing (120) the radio network node (12) from operating in any of the determined sleep modes; the invention further refers to a corresponding network node and a computer program.