An agricultural machine for forage harvesting, including a frame supporting a work unit able to occupy a work position in which it can pick up plants lying on the ground and shift them sideways, a side deflector being connected to the frame by a connecting device allowing the deflector to occupy an operation position relative to the work unit, in which the deflector can receive a flow of plants shifted sideways by the work unit. The connecting device is designed so that, while the machine moves in a direction and the work unit is in the work position, the deflector can perform a movement relative to the work unit from the operation position, longitudinally in a direction opposite the movement direction, when a resultant of a force exerted on the deflector exceeds a determined threshold.
