The invention relates to an internal gear pump for a brake system, in the pump housing of which an internally toothed ring gear and a pinion meshing with the toothing of the ring gear are pivotally supported about parallel axes. As a result the toothing thereof limits an approximately crescent-shaped tapering annular space, in which a filler piece supported toward the intake side of the pump is arranged. The circumferential sides of the filler piece are bent in accordance with the addendum circle of the ring gear toothing or of the pinion toothing. The sides rest against several tooth tips in a sealing manner under a spring force. According to the invention, one of the two circumferential sides of the filler piece is formed by a radially resilient circumferential wall, which is nestled against the tooth tips of the pinion or the ring gear due to the deflection based on the inherent spring force thereof.