The invention relates to an isolated driver (100) for lighting means (109), comprising: a primary circuit (100a), a secondary circuit (100b), an isolation barrier (106) separating the primary circuit (100a) and the secondary circuit (100b), wherein a ground potential of the primary circuit (100a) and a ground potential of the secondary circuit (100b) are connected via a capacitor (107), and a control circuit (111) on the secondary side (100b), monitoring a current to/from the capacitor (107) to the ground potential of the secondary circuit (100b) and issuing a mains (101) failure signal in case the current does not meet predefined conditions, preferably in case no such current is detected.