A master cylinder includes a restraining device arranged between the first and second pistons for preventing the return spring from being compressed and expanded beyond a certain extent. The restraining device includes a first, substantially sleeve-shaped component and a second, substantially pin-shaped component. The pin-shaped component includes a flange which projects radially outwards. The sleeve-shaped component includes a first receiving flange which positively interacts with the flange of the pin-shaped component. The sleeve-shaped component includes at least one introduction opening which enables the flange on the pin-shaped component to be laterally introduced into the sleeve-shaped component. The end of the sleeve-shaped component includes a second receiving flange which positively interacts with a flanged projection on the second piston which projects radially outwards. The sleeve-shaped component includes the at least one introduction opening which enables the flange provided on the second piston to be laterally introduced into the sleeve-shaped component.