An air filter for an for an air intake of an internal combustion engine. The filter includes a housing with a raw air inlet and a clean air outlet and an annular filter element having a pleated filter medium disposed therein. At least one buttressing element is provided to support the filter medium at the clean air side. The buttressing element has a knife-edge buttress disposed on the housing that extends to a position of maximum flexure of the filter element. The knife-edge buttress is further provided with a support shoe disposed thereon such that the shoe supports the filter element.