A compressor section includes a shroud surface and a rotor with a blade tip that opposes the shroud surface. The rotor is configured to rotate within the shroud about an axis of rotation. Moreover, the compressor section includes a serration groove that is recessed into the shroud surface. The serration groove includes a forward portion with a forward transition and a forward surface that faces in the downstream direction. The forward transition is convexly contoured between the shroud surface and the forward surface. The serration groove includes a trailing portion with a taper surface and a trailing transition. The taper surface tapers inward as the taper surface extends from the forward surface to the trailing transition. The trailing transition is convexly contoured between the taper surface and the shroud surface.