XML-based file format must be validated against its DTD in order to be visualised. In cooperative editing, the replication of XML documents in different sites allows to ameliorate the availability of data. After the reconciliation of the different replicas of the initial document, it is possible that the result of the merging does not validate the DTD. This means that it is not possible to open the document with the tool that edits it. To overcome this problem, we propose an automatic repairing approach in order to re-establish the consistency of XML documents.