A method for controlling a filling of an exhaust-gas component storage-device of a catalytic-converter in the exhaust-gas of an internal-combustion-engine, in which an actual fill level (θmod) of the exhaust-gas component storage-device is ascertained using a first-system model to which signals (λin,meas) of a first-exhaust-gas probe that extends into the exhaust-gas flow upstream from the catalytic-converter and that acquires a concentration of the exhaust-gas component are supplied, if this first exhaust-gas probe is ready for operation. A lambda-target-value (λin,set) for a first control-loop is specified by a lambda-target-value pilot control, and that, if the first exhaust-gas probe is not ready for operation, a replacement signal for the signal of the first exhaust-gas probe is supplied to the system-model, and the replacement signal is used in the lambda-target-value pilot control as an initial-value for the lambda-target-value. Also described is a control device for the method.