Abstract-Multi-tenancy is a relatively new software architecture principle in the realm of the Software as a Service (SaaS) business model. It allows to make full use of the economy of scale, as multiple customers -"tenants" -share the same application and database instance. All the while, the tenants enjoy a highly configurable application, making it appear that the application is deployed on a dedicated server. The major benefits of multi-tenancy are increased utilization of hardware resources and improved ease of maintenance, resulting in lower overall application costs, making the technology attractive for service providers targeting small and medium enterprises (SME). Therefore, migrating existing single-tenant to multi-tenant applications can be interesting for SaaS software companies. In this paper we report on our experiences with reengineering an existing industrial, single-tenant software system into a multitenant one using a lightweight reengineering approach.