In a method for controlling a vehicle with a drive system comprising a power unit configuration adapted to provide output for the vehicle's operation, and further comprising a planetary gear and a first and second electrical machine, connected to components in the planetary gear via their rotors, a locking means is moved from a locked position, in which two of the planetary gear's components are locked together, so that the three components of the planetary gear rotate with the same speed, to a release position, when the vehicle is driven with the locking means in a locked position, by carrying out the following method steps. The power unit configuration is controlled in order to achieve torque balance between the components that are locked together by the locking means, and such locking means are moved into a release position, when said torque balance prevails.