The invention relates to a security device for a plug (1) with at least one locking clip (2) said security device comprising a lockable closure piece (8, 12) which prevent the manual operation of the locking clip (2). The closure piece (8, 12) comprises a closure lower piece (8) which may be fixed to the plug (1) on which a separate closure upper piece (12) is placed. Said closure lower piece (8) is designed such as to be clipped on the plug (1) with a positive and/or non-positive fit.