It is described a method of estimating a value (25) of wind speed a wind turbine (1) is subjected to, the wind turbine having a rotor (3) with rotor blades (5) at least one having an adaptable flow regulating device (7) installed, the method comprising: obtaining values (23) for power output of the wind turbine, rotor speed of the rotor (3), and pitch angle of the rotor blades (5); obtaining state information (13) of the adaptable flow regulating device (7); and estimating the value (25) of the wind speed based on the values (23) for power output, rotor speed, pitch angle and the state information (13) of the adaptable flow regulating device (7).