A casing (1) for a rotating machine, comprising a first segment (12) which is fixed and a second segment (14) which rotates about an axis of rotation (X-X), the first segment (12) and the second segment (14) being in contact along an interface provided with a sealing element (40), said sealing element (40) being positioned in a housing (30) connected to the internal volume of the casing on one hand and to the ambient environment on the other hand, the connection between the housing (30) and the ambient environment being produced via a conduit (50), characterized in that the first casing segment (12) or the second casing segment (14) comprises a planing portion (60) positioned at an outer end of the conduit (50).