A method of controlling a transmission brake of an automated change-speed transmission, of a countershaft design provided with claw clutches, the brake being functionally connected, on its input side, to a transmission shaft and actuated hydraulically or pneumatically by way of inlet and outlet valves such that, for an upshift from a gear under load to a target gear, when the loaded gear is disengaged, in order to synchronize the target gear, first the inlet valve is opened and the outlet valve is closed, then to produce a substantially constant braking torque, the inlet valve is closed after having been open for a determinable opening duration, and to reach a synchronous rotational speed, the outlet valve is opened after having been closed for a determinable closing duration. The time during which the inlet valve is open is determined as a function of a specified characteristic parameter of the synchronization process.