A rotor blade of a wind turbine, wherein the rotor blade includes a lift modifying device, is provided. The lift modifying device is a part of the trailing edge section of the rotor blade. The lift modifying device is configured such that, at a predetermined loading of the trailing edge section, an air channel opens up a flow path from the pressure side to the suction side and vice versa in the trailing edge section. As a consequence, airflow flowing from the leading edge section of the rotor blade to the trailing edge section is at least partly deflected by the open air channel, which results in a modification of the lift of the rotor blade. A method to modify the lift of a rotor blade of a wind turbine is also provided.