Exchange 2013 - Distribution group owner to add/remove members

We recently moved from Exchange 2007 to Exchange 2013 and now our users can no longer add/remove members of existing distribution groups that they are owners of and could do so previously. I added the user as Owner into the Distribution Group - Ownership and they still cannot do so. Clearly I'm looking in the wrong place or have missed something.

I should also add that we are on Exchange 2013 - CU2.