the invention relates to a luminaire with at least one led as luminous means and a method for operating the luminaire . the luminaire has a sensor for detecting at least a part of the light emitted by the led and also a control unit for evaluating the sensor signals and for influencing the led in a manner dependent on the sensor signals . after the luminaire has been switched on , a specific led current flows and the light intensity of the led is checked . in the case of a light intensity below a reference value , the led current is raised by a defined value .