A device for locking a rotor blade of a wind turbine which has an adjustment system for the blade pitch angle of the rotor blade, wherein the adjustment system has a drive which features a motor and a gearbox with an input shaft that bears an external toothing, characterized by a locking pin rotatably mounted around its longitudinal axis, which engages with the external toothing in a locking position, and releases the external toothing in an unlocked position, wherein the locking pin has an end portion whose free end stands eccentric to the longitudinal axis of the locking pin.