Method for operating a brake system

A method for operating a brake system, which includes a power brake and a vehicle dynamics control, after detecting that the level in a brake fluid reservoir of the brake system has fallen below a minimum fill level. The method includes detecting a brake signal, advancing a power piston to a forward position in which the required brake pressure is achieved, ascertaining the amount of travel of the power piston from the home position to the current position, holding the brake pressure and further advancing the power piston by a correction distance if the brake pressure decreases during the holding. The method also includes retracting the power piston by the ascertained amount of travel after the braking process has ended and degrading the brake system when a limit value for the forward position of the power piston has been reached.