An internal combustion engine comprising: - an engine block having a plurality of piston-cylinder units in which in operation of the internal combustion engine an air-fuel mixture is combustable with the production of exhaust gases containing an NO x portion, wherein there is provided an engine closed-loop control unit for controlling operation of the engine block, and - an exhaust gas aftertreatment apparatus for aftertreatment of the exhaust gas occurring in operation for reduction at least of the NO x portion, wherein the exhaust gas aftertreatment apparatus has at least one SCR catalytic converter, and - a catalytic converter closed-loop control device for open-loop or closed-loop control at least of the at least one SCR catalytic converter, wherein the engine closed-loop control unit is given a target value ( NO x, Tar) for an NO x average value ( NO x) of the NO x portion of the exhaust gases, that occur in relation to a predetermined period of time (t av) at a discharge from the exhaust gas aftertreatment apparatus, and wherein the engine closed-loop control unit is configured at least in one operating mode to take account in cumulated form of already emitted NO x portions of the exhaust gas since the beginning (t 1) of the period of time (t av), characterized in that - the engine closed-loop control unit is configured to continuously calculate an NO x reference value ( NO x, Ref ( t)) for the catalytic converter closed-loop control device having regard to already emitted NO x portions and the predetermined target value ( NO x, Tar), which reference value is so selected that at the end of the predetermined period of time (t av) the predetermined target value ( NO x, Tar) results at the discharge of the exhaust gas aftertreatment apparatus, and - the calculated NO x reference value (NO x, Ref (t)) is fed to the catalytic converter closed-loop control device as an NO x setpoint value. - an engine block having a plurality of piston-cylinder units in which in operation of the internal combustion engine an air-fuel mixture is combustable with the production of exhaust gases containing an NO x portion, wherein there is provided an engine closed-loop control unit for controlling operation of the engine block, and - an exhaust gas aftertreatment apparatus for aftertreatment of the exhaust gas occurring in operation for reduction at least of the NO x portion, wherein the exhaust gas aftertreatment apparatus has at least one SCR catalytic converter, and - a catalytic converter closed-loop control device for open-loop or closed-loop control at least of the at least one SCR catalytic converter, wherein the engine closed-loop control unit is given a target value ( NO x, Tar) for an NO x average value ( NO x) of the NO x portion of the exhaust gases, that occur in relation to a predetermined period of time (t av) at a discharge from the exhaust gas aftertreatment apparatus, and wherein the engine closed-loop control unit is configured at least in one operating mode to take account in cumulated form of already emitted NO x portions of the exhaust gas since the beginning (t 1) of the period of time (t av), characterized in that - the engine closed-loop control unit is configured to continuously calculate an NO x reference value ( NO x, Ref ( t)) for the catalytic converter closed-loop control device having regard to already emitted NO x portions and the predetermined target value ( NO x, Tar), which reference value is so selected that at the end of the predetermined period of time (t av) the predetermined target value ( NO x, Tar) results at the discharge of the exhaust gas aftertreatment apparatus, and - the calculated NO x reference value (NO x, Ref (t)) is fed to the catalytic converter closed-loop control device as an NO x setpoint value. - the engine closed-loop control unit is configured to continuously calculate an NO x reference value ( NO x, Ref ( t)) for the catalytic converter closed-loop control device having regard to already emitted NO x portions and the predetermined target value ( NO x, Tar), which reference value is so selected that at the end of the predetermined period of time (t av) the predetermined target value ( NO x, Tar) results at the discharge of the exhaust gas aftertreatment apparatus, and - the calculated NO x reference value (NO x, Ref (t)) is fed to the catalytic converter closed-loop control device as an NO x setpoint value.