Thanks Ivan, Here are the steps I took to reproduce the issue on a new project I started. I've also added a few screen shots. 1. Add Classification 2. Add a few test publication types 3. Add a new library 4. Upload a document (I only do this because I can't find a way to get to the Custom Field without creating a document and getting to the listings page) 5. Add Custom Field at /Sitefinity/Content/Documents 6. Try adding a new document, error will be thrown.