Business-critical legacy applications often rely on relational databases to sustain daily operations. Introducing Semantic Web technology in newly developed systems is often difficult, as these systems need to run in tandem with their predecessors and cooperatively read and update existing data. A common pattern is to incrementally migrate data from a legacy system to its successor by running the new system in parallel, with a data bridge in between. Existing approaches that can be deployed as a data bridge in theory, restrict Semantic Web-enabled applications to read legacy data in practice, disallowing update operations completely. This paper explains how our RDB-to-RDF platform OntoAccess can be used to transition legacy systems into Semantic Web-enabled applications. By means of a case study, we exemplify how we successfully made a bridge between one of our own large-scale legacy systems and its long-term replacement. We elaborate on challenges we faced during the migration process and how we were able to overcome them.