A filling of an exhaust gas component storage of a catalytic converter is regulated. An actual fill level of the exhaust gas component storage is ascertained using a first system model, and a base lambda setpoint value for a first control loop is predefined by a second control loop. An initial value for the base lambda setpoint value is converted into a fictitious fill level, the fictitious fill level being compared with a setpoint value for the fill level output, and the base lambda setpoint value being iteratively changed as a function of the comparison result, if a difference between the setpoint value for the fill level and the fictitious fill level is greater than a predefined degree. The base lambda setpoint value is not changed if no difference exists between the setpoint value for the fill level and the fictitious fill level.