The invention relates to a fastening element (1) for fixing to a mounting rail (4), wherein the fastening element (1) comprises an anchoring body (9) for engaging in the mounting rail (4) which is axially adjustable with a threaded element (2) connected, extending along a longitudinal axis (LB) in the axial direction and a spring element (14) and a support element (5) for bearing on the mounting rail (4) or on an attachment part (17) passing through. The support element (5) is movable toward a mounting position axially to the anchor body (9). In order to allow users an easy way to check the correct mounting of the fastening element (1), it is proposed that the fastening element (1) has a marking element (26) is arranged such that it is relative to the support element (5) moves when the support element (5) is axially moved to the anchor body (9).