The invention provides, in one aspect, a pneumatic fastener driver including a cylinder and a piston positioned within the cylinder. The piston is moveable between a top-dead-center position and a bottom-dead-center position. The driver also includes a magnetic latch emitting a magnetic field that magnetically attracts the piston and is capable of holding the piston in the top-dead-center position with a magnetic force. The magnetic latch is adjustable to vary the magnetic force acting on the piston for driving fasteners into a workpiece at different depths.