Radio display only works with headlights

Recently bought this car second hand. The audio on the radio works absolutely fine, but the buttons on the face of the radio do not work or light up and the display does not light up either. The volume can still be adjusted by the steering wheel buttons. However, when the headlights are turned on, the radio display turns on and comes to life, showing 1:00, and the buttons also light up and begin working. I am entirely clueless as to what could be causing this, except for some sort of error with the twelve volts constant.