A portable linear fastener driving tool is provided that drive staples, nails, or other linearly driven fasteners. The tool uses a gas spring principle, in which a cylinder filled with compressed gas is used to quickly force a piston through a driving stroke movement, while a driver also drives a fastener into a workpiece. The piston/driver is then moved back to its starting position by use of a rotary-to-linear lifter, and the piston again compresses the gas above the piston, thereby preparing the tool for another driving stroke. An improved lifter design has modified lifting pins that reduce the side-forces on the driver. A pivotable latch acts as a safety device, by preventing the driver from making a full driving stroke at an improper time. An improved latch design has a more durable catching surface.