The present paper proposes to offer some brief reflections, in general terms, on the role of the judge with reference to the contract and, in particular, on its modalities of intervention in the event of invalidity, pursuant to and for the effects of art 1424 civ. cod. In this sense it recalls the doctrinal debate on functional profiles and on the legal nature of the institute of the conversion of the null contract. The author seems to agree with that interpretative option that see art 1424 civ. cod. as an interpretative canon of the contract (invalid) that juxtaposes to those provided for in Chapter IV of the Book IV to arts 1362 et seq. civ. cod. In this perspective, the conversion of the null contract is placed between the instruments for the ?just remedy?, independently of the specific indications of the procedural parties, thus finding in the system the most appropriate solution to implement and compose conflicting interests, respecting the values of the legal system.