The present invention relates to a method for adapting a ground fault detection to a change of an electrical machine condition, wherein the machine includes a winding. The electrical machine is in a first machine condition, a first reference value being defined for measured values of an electrical quantity. The ground fault detection comprises continuously measuring the electrical quantity in the winding and detecting a ground fault based on the measured values of the electrical quantity and the first reference value. The method comprises receiving a signal (101, 102), detecting a change of machine condition based on the received signal (120), and changing to a second reference value for the measured values of the electrical quantity, the second reference value being different from the first reference value (100) when the change of machine condition is detected.