A lighting device and a method for operating a discharge lamp are described. In one embodiment, the discharge lamp comprises a sealed discharge vessel and two electrodes to produce an arc. A driver circuit delivers electrical power to the electrodes. In a run-up interval, electrical power is supplied as an alternating current IL. During the run-up interval, the waveform of the alternating current IL is changed at least once to a spot-enforcing waveform in order to change the mode of attachment of the arc to the electrodes to spot mode.