How to delete inherited properties in DocumentType

Questions
1

For example:

I have to document types:

DocType1
               |----DocType2

DocType1 has Property1, so DocType inherits it.

When I installed new version 4.0.3 I could delete the Property1 from DocType2, but after upgrade from 4.0.2.1 I can't do it.

Please help! :)

This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/6527-how-to-delete-inherited-properties-in-documenttype