A method of reducing the load of a rotor blade of a wind turbine during installation of the wind turbine, whereby the rotor blade includes an aerodynamic device such as a vortex generator or a noise reducer is provided. The method includes the steps of attaching a cover on the rotor blade for covering at least a part of the aerodynamic device before lifting the rotor blade to the top of the tower of the wind turbine, and detaching the cover subsequently. An arrangement including a rotor blade of a wind turbine and such a cover, is also provided.