Why has base class protection been deprecated?

[David Bryant]

With the dmd 2.059 I have started getting the error 'use of base class 
protection is deprecated' when I try to implement an interface with 
private visibility, ie:

   interface Interface { }

   class Class : private Interface { }

  $ dmd test.d
  test.d(4): use of base class protection is deprecated

This bothers me for two reasons: firstly it's not a base class, and 
secondly, it's a standard OO pattern of mine.

What's up with this?

Thanks,
Dave