A filter assembly includes housing enclosing a replaceable filter element. A support core is provided in the housing, and includes an extension and locking assembly. The element includes a ring of filtration media with a pair of end caps. The first end cap includes a central opening to receive the support core. The extension and locking assembly prevents the cover of the housing from being attached to the housing body without a proper filter element installed. The extension and locking assembly includes a bypass member and a locking member, which are in locking engagement when an element is absent in the housing. The second end cap includes internal protrusions which engage the locking member when the filter element is installed to disengage the bypass member from the support core, and allow the element to be inserted and the cover to be installed.