A turbocharger and a method are disclosed. The turbocharger includes a casing having an inlet end and an outlet end. A flow passage within the casing may have a substantially continuous inner surface and may be configured to pass inlet air from the inlet end to the outlet end. A compressor wheel may be located in the casing and may have at least one main blade and may be configured to rotate within the casing to compress the inlet air. A flow disrupting feature on the casing may be configured to disrupt the continuity of the inner surface and may be located at a leading edge of the at least one main blade. The flow disrupting feature may be closed to upstream communication with the flow passage except via the flow passage.