AssertionError raised when bulk creation model with composite primary key

[Will-Ruddick]

I have a model that looks something like this

class CompositeModel(models.Model):
    pk = models.CompositePrimaryKey("other_model", "the_time", "created_at")

    other_model = models.ForeignKey("test.OtherModel", on_delete=models.CASCADE)
    the_time = models.DateTimeField()
    created_at = models.DateTimeField(auto_now_add=True)

And when I try and bulk create it in the code I get the following exception.

    CompositeModel.objects.bulk_create(new_items)
  File "django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "django/db/models/query.py", line 836, in bulk_create
    assert len(returned_columns) == len(objs_without_pk)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError

Where returned_columns is an empty list and objs_without_pk is a list of the objects I'm trying to create.

If I use ignore_conflicts=True then everything works fine and the objects are created properly in the DB. I think this is a bug, but it could be user error.

This is happening on version 5.2.5