"Required" validator on "hippo:resource" does not work

1. Login to CMS as admin
2. Navigate to documents >> configuration >> hippogogreen >> simpledocument
3. Edit and add a resource item from "compound field", mark it as mandatory
---- A star should appear on the resource filed
4. Now go back to documents and create a document using simple document type
5. Do not have any value in the newly added "resource" field
6. Save & Close the document

Actual - User is able to save the document
Expected - User should be prompted with empty value in "Resource" field