The invention relates to a connecting sleeve for anchoring shafts of two oppositely arranged prostheses, preferably on an elongate bone such as a femur or humerus. The reinforcing sleeve comprises two receiving bushes (1, 2) for one prosthesis shaft each and comprises a separable coupling region (3) arranged therebetween for connection in such a manner as to resist shear forces and rotation. According to the invention, each receiving bush (1, 2) has, on the side thereof facing the coupling region, one fork (31, 32) of a pair of forks that interact with each other, and a fitting block (4) is arranged on a base of the fork, the lateral surfaces (44) of which fitting block have a distance that corresponds to an inner width of the fork, and the lateral surfaces (44) are designed to contact flanks of the fork in a planar manner, at least one fastening screw (5) being arranged transversely through the fork. The fork connection is simpler to produce than the known wedge connection and yet is sufficiently robust. Unlike in the case of the wedge connection, an exact fit is not required; a clearance fit between the fork (31, 32) and the fitting block (4) is sufficient in principle, excessive play being eliminated by means of the fastening screw (5).