A method is detect inadequate valve seat integrity in a control element of a control valve is proposed, wherein during a calibration time interval the position of the control element of the control valve in the closed position are repeatedly measured and recorded. Measuring of the position in the closed position continues during operation, and a moving average value is determined over a specified number of values. A threshold is determined from the calibration data set and the specified number. If the moving average deviates from the average of the calibration data by more than this threshold, a message is output. In particular, no additional sensors or scanning devices are required and a sensible compromise between early fault detection and avoidance of false diagnoses is achieved.