This augment insert (200), comprises a coupling member (204) for securing the augment insert to a glenoid component (103) of a shoulder prosthesis (101), and a body (202), comprising a first side (206), configured to bear against a scapular side (107) of the glenoid component when the augment insert is secured to the glenoid component by means of the coupling member; and a second side, opposed to the first side and configured to bear against or be adjacent to a scapula of a patient. According to the invention, the body (202) comprises at least one breakable portion (230), extending from the first side (206) to the second side and configured to be broken off the body. The aperture (234) is provided for accommodating an engaging member (111) of the glenoid component (103), said engaging member protruding from a scapular surface (127) of the scapular side (107) of the glenoid component (103) and being configured for securing the shoulder prosthesis to the scapula.