While testing with hibernate 5 I also made some more tests and can say that the second case is not so bad after all. The @MapKeyColumn is not honored which is a bug, but value corresponds to the map key column and hash is added (probably for some internal reason). Both value and hash can be overriden with

@AttributeOverride(name="key.hash", column=@Column(name="myhashcol"))
@AttributeOverride(name="key.value", column=@Column(name="mykeycol"))

The first case (map with enumeration type as key) still misses the key column regardless of whether the @MapKeyEnumerated is present or not.