Apparatus for controlling a current flowing through an illumination source, the apparatus comprising: current measurement circuitry arranged to take a current measurement (I LEDf ) measuring the current flowing through the illumination source (I LED ); a current controller configured to output a current control signal (I ctrl ) to control the current flowing through the illumination source, and thereby control an amount of illumination emitted by the illumination source; power circuitry arranged to receive the current control signal (I ctrl ) and in dependence thereon to drive the current flowing through the illumination source, the current controller being configured to adjust the current control signal (I ctrl ) based on an error signal (I err ) representing a comparison between an input set-point (I ref ) and the current measurement fed back from the current measurement circuitry , order to thereby keep said current flowing through the illumination source on average substantially steady at a level specified by said input set-point (I ref ); characterized in that the apparatus further comprises: a coded light injector arranged to modulate the current control signal (I ctrl ) output by the current controller in order to cause a sequence of data symbols to be modulated into the current flowing through the illumination source, and to thereby cause the sequence of data symbols to be embedded in the emitted illumination; and a compensation filter arranged to receive an indication of a presently transmitted data symbol (I data ) and apply a compensation (I af ) to the error signal (I err ) based thereon, to at least partially remove an effect of a distortion of the current measurement caused by the modulation of the data symbols into said current flowing through the illumination source (I LED ) by means of the compensation (I af ). current measurement circuitry arranged to take a current measurement (I LEDf ) measuring the current flowing through the illumination source (I LED ); a current controller configured to output a current control signal (I ctrl ) to control the current flowing through the illumination source, and thereby control an amount of illumination emitted by the illumination source; power circuitry arranged to receive the current control signal (I ctrl ) and in dependence thereon to drive the current flowing through the illumination source, the current controller being configured to adjust the current control signal (I ctrl ) based on an error signal (I err ) representing a comparison between an input set-point (I ref ) and the current measurement fed back from the current measurement circuitry , order to thereby keep said current flowing through the illumination source on average substantially steady at a level specified by said input set-point (I ref ); characterized in that the apparatus further comprises: a coded light injector arranged to modulate the current control signal (I ctrl ) output by the current controller in order to cause a sequence of data symbols to be modulated into the current flowing through the illumination source, and to thereby cause the sequence of data symbols to be embedded in the emitted illumination; and a compensation filter arranged to receive an indication of a presently transmitted data symbol (I data ) and apply a compensation (I af ) to the error signal (I err ) based thereon, to at least partially remove an effect of a distortion of the current measurement caused by the modulation of the data symbols into said current flowing through the illumination source (I LED ) by means of the compensation (I af ). <EOS>