Lookup of attribute 'id' on model inheritance models in InlineModelAdmin fails when using fk_name of parent model

[Waldemar Hamm]

Having two models, of which one inherits from another, for example:

class Person(models.Model):
    firstname = models.CharField(max_length=255, blank=True)
    lastname = models.CharField(max_length=255)
    person_something = models.ForeignKey(Something)

class Author(Person):
    publisher = models.CharField(max_length=255)
    author_something = models.ForeignKey(Something)

I can't access the id field like so:

class AuthorInline(admin.StackedInline):
    model = Author
    fk_name = 'person_something'
    fields = ['id', 'lastname', 'publisher']

class SomethingAdmin(admin.ModelAdmin):
    resource_class = Something
    inlines = [ AuthorInline ]
    list_display = ('somethinga', 'somethingb')

I get a KeyError and it says:
"Key 'id' not found in 'AuthorForm'"

Using Author._meta.get_all_field_names() the field id is definitely in the model, though. Removing 'id' from the fields list makes everything work.

Am I doing something wrong or is this a legit bug?