A fast automated gear shift operation is performed using a powertrain in a hybrid vehicle, the powertrain including a gear box, an engine, at least one controllable motor, a torque ripple damping device, a mechanical connecting device for connecting or disconnecting the engine to or from, respectively, wheels of the vehicle. In the gear shift operation the motor is controlled to perform a sequence of steps in which different torques are delivered by the motor to temporarily change the speed thereof. The torques are selected so that they to reduce the mechanical tension over at least one elastic part of the powertrain. Hence it can be achieved, that during at least a period during the gear shift operation torques over mechanical elements in the gear box cooperating in the current gear and/or over the mechanical connecting device are eliminated or at least strongly reduced. The period should be sufficiently long so as to permit disconnection of said mechanical elements cooperating for the present gear and/or to permit disconnection of the mechanical connection device.