The urgent demand for supporting teamwork and continuous evolution of software models triggered intensive research on optimistic version control systems for models. State-of-the-art model versioning approaches primarily focus on detecting changes and conflicts between concurrently evolved versions of a model. However, techniques for conflict visualization have been hardly investigated yet. In this paper, we propose to support the visualization of conflicts in the concrete syntax of UML models. For this purpose, we present an approach to tentatively merge concurrently evolved versions of one model featuring all performed changes, yet keeping conformance to the UML metamodel. Changes and conflicts are visualized in this tentatively merged model without requiring any editor extensions. Instead, we employ the powerful profile mechanism of UML to enable modelers to resolve conflicts within their favorite UML editor.