A pyrotechnic pretensioner (10) for a safety system in a vehicle has an inflator (22) including a propelling charge (26) and an igniter (32) and including a housing (12) in which a pressure chamber (14) is provided into which gas can flow and in which a piston can be displaced by the gas, an end piece (16) which closes the pressure chamber (14) and in which a chamber (24) is formed into which the propelling charge (26) is filled and whose wall constitutes the wall of the propellant is provided on the housing (12).