A method of preventing inadvertent inflation of an implantable prosthetic includes biasing a valve assembly such that an outlet is substantially closed and using inadvertent pressure increases from the inlet to supplement the biasing of the valve assembly. It may further include the step of preventing fluid flow through the outlet by selectively varying fluid pressure within a bypass passageway having a first end which is in fluid communication with an inlet and a second end which is in fluid communication with a chamber. And, may also additionally include the step of displacing a flexible abutting wall disposed between the chamber and the valve assembly so that the abutting wall is caused to contact the valve assembly and urge the valve assembly into a closed position when the fluid pressure within the chamber exceeds a predetermined amount.