A safety device for closure elements (1) on pressure-medium-containing tanks, in particular on hydropneumatic devices such as hydraulic accumulators, has a screw connection provided as a closure device on a filling or checking port. The screw connection has a closure screw (1) threadedly engaged on the port (3) and blocking the port (3) when the screw connection is tightened and opens the port (3) when a flow path is released. A device (25) limits the free movement path of the closure element (1) when moved out of a closed position as a result of occurring overpressure.