A method is provided for operating an internal combustion engine in whose exhaust-gas region an exhaust-gas treatment device is situated, and in which a reagent is introduced into the exhaust-gas region of the internal combustion engine. in addition, a device is provided for implementing the method. The reagent pressure occurring between a reagent safety valve and a reagent dosing valve, disposed directly in the exhaust-gas region is recorded during different states of the reagent safety valve and/or the reagent dosing valve and compared to at least one threshold value. If the threshold is exceeded, a fault signal is provided. This may offer high safety which may be of particular importance when fuel is used as reagent.