Method for regulating stable operation of an exhaust-gas turbocharger of an internal combustion engine having a fresh-gas supply device, a switchover valve, a control device, a compressor and an air-processing unit with a discharge valve, having the following method steps: - operating the compressor in a suction intake mode, wherein the switchover valve connects the compressor to an air inlet, and monitoring operating parameters of the internal combustion engine, of the air-processing unit and of the exhaust-gas turbocharger; - regulating stable operation of the exhaust-gas turbocharger on the basis of the monitored operating parameters by switching over the compressor from the suction intake mode to a pressure-charged mode, with the switchover valve connecting the compressor to a compressor of the exhaust-gas turbocharger, wherein operation of the fresh-gas supply device forms a monitored operating parameter; and - switching over the compressor on the basis of the monitored operating parameters from the pressure-charged mode into the suction intake mode, with the switchover valve connecting the compressor to the air inlet again, wherein the method step of regulation has the following component steps: - monitoring a boost pressure and/or a mass flow of the compressor of the exhaust-gas turbocharger; and - connecting the outlet of the compressor to the atmosphere by opening the discharge valve if a mass flow diverted from the compressor of the exhaust-gas turbocharger into the compressor is still too small in the pressure-charged mode of the compressor, wherein an air path for the discharge of the air mass flow from a charge-air line through the compressor and through the discharge valve into the atmosphere is formed, and pumping of the exhaust-gas turbocharger is prevented. - operating the compressor in a suction intake mode, wherein the switchover valve connects the compressor to an air inlet, and monitoring operating parameters of the internal combustion engine, of the air-processing unit and of the exhaust-gas turbocharger; - regulating stable operation of the exhaust-gas turbocharger on the basis of the monitored operating parameters by switching over the compressor from the suction intake mode to a pressure-charged mode, with the switchover valve connecting the compressor to a compressor of the exhaust-gas turbocharger, wherein operation of the fresh-gas supply device forms a monitored operating parameter; and - switching over the compressor on the basis of the monitored operating parameters from the pressure-charged mode into the suction intake mode, with the switchover valve connecting the compressor to the air inlet again, wherein the method step of regulation has the following component steps: - monitoring a boost pressure and/or a mass flow of the compressor of the exhaust-gas turbocharger; and - connecting the outlet of the compressor to the atmosphere by opening the discharge valve if a mass flow diverted from the compressor of the exhaust-gas turbocharger into the compressor is still too small in the pressure-charged mode of the compressor, wherein an air path for the discharge of the air mass flow from a charge-air line through the compressor and through the discharge valve into the atmosphere is formed, and pumping of the exhaust-gas turbocharger is prevented.