Abstract: A gas spring is described, which comprises a first part which defines a cylinder, which comprises a longitudinal axis and which is closed at a first end along the longitudinal axis. The gas spring further comprises a piston, which is arranged to be movable along the longitudinal axis in the cylinder, a piston rod which is connected to the piston and which projects out through a second end of the cylinder, a separating piston which is arranged to be movable in the cylinder along the longitudinal axis between the piston and the first, gas which is contained in the cylinder between the separating piston and the first, and liquid which is contained between the separating piston and the piston.