faces-config.xml does not open in dedicated config editor (Diagram, Tree, Source)

I created a JSF project using the JSF project wizard. When I double-click on the faces-config.xml file it opens in a dedicated editor with diagram, tree and source views. Great

I was then looking at enabling the JSF facet on an existing basic project. A faces-config.xml file was created. Again, I double-clicked to open it but it opened in a plain editor. I tried right-clicking on the file and clicking Open With>Other and selecting some of the JBoss editors but couldn't get it to open in the dedicated editor.