A control device for a vehicle brake system, having a control device/arrangement by which a closing signal is outputtable to an isolation valve via which a first brake circuit is hydraulically connected to a main brake cylinder, and at least one first control signal is outputtable to at least one first hydraulic component, so that a first actual brake pressure in the first brake circuit can be varied, an existing functional impairment of the at least one first hydraulic component and/or of at least one further brake system component being determinable, or a warning signal being receivable, and, if warranted, a closing signal being outputtable to a changeover valve of a second brake circuit, and, after or simultaneously with an outputting of the closing signal to the changeover valve, an opening signal being outputtable to the isolation valve. Also described is a related method for operating the vehicle brake system.