A method for operating a system having an internal combustion engine and an exhaust aftertreatment system having an SCR catalyst, wherein the internal combustion engine is controlled on the basis of at least one process parameter that influences a nitrogen oxide raw emission, wherein aging detection is performed for the SCR catalyst, wherein in a first operating mode of the internal combustion engine, if aging of the SCR catalyst is detected, the at least one process parameter is changed in the direction of a reduced nitrogen oxide raw emission, wherein the internal combustion engine is controlled on the basis of the changed at least one process parameter.