The present invention relates to a wind turbine (1) and a method of operating a wind turbine with at least one rotational speed exclusion zone (18, 19), wherein the wind turbine (!) comprises a wind turbine control system (10) monitoring the vibrations of the wind turbine tower (2) and the rotational speed of the rotor. The wind turbine control system (10) controls the rotational speed of the rotor based on the measured vibration level (13), wherein the control system (10) uses the at least one exclusion zone (18, 19) to avoid rotational speeds that coincide with the eigenfrequency (14) of the wind turbine tower (2). The at least one exclusion zone (18, 19) has a variable width, which is determined based on the measured vibration level (13) so that resonance in the wind turbine tower (2) is avoided while minimizing the power loss.