A method of controlling a transmission brake of an automated change-speed transmission having a control cylinder, that is pressurized by inlet and outlet valves, and an upstream main cut-off valve by which a nominal pressure, supplied to the control cylinder, is regulated. Functional deviations of the transmission brake can be considered during a shifting operation, when the transmission is in neutral, the motor coupling clutch is disengaged and the transmission brake is engaged. The rotational speed gradient and the mass of the transmission components to be braked are determined and used to calculate the current braking torque of the transmission brake. The current braking torque relates to the current regulated nominal pressure, and the determined values are stored in a control unit and used during subsequent actuation of the transmission brake.