A compression-ignition engine (10) comprises an exhaust system (16) with an exhaust gas after-treatment assembly, the after-treatment assembly comprising a three-way catalyst device (30) and an SCR device (34), the three-way catalyst device being arranged upstream the SCR device in close-coupled position with respect to the engine. An engine control unit (47) is provided for controlling operation of the engine. The engine control unit is configured to monitor the temperature of the SCR device and to control the engine to change over from an operation with a lean air/fuel mixture to an operation with a stoichiometric or a rich air/fuel mixture in response to the temperature of the SCR device dropping below a temperature threshold.