Index.document() doesn't set index on Document on elasticsearch-dsl-py>=6.3.0

[sir-sigurd]

This code worked on elasticsearch-dsl-py==6.2.1

from elasticsearch_dsl import Index, Document, Text

i = Index('blog')

@i.document
class Post(Document):
    title = Text()

Post().to_dict(include_meta=True)

But on elasticsearch-dsl-py>=6.3.0 error is raised:

ValidationException                       Traceback (most recent call last)
<ipython-input-11-0a92233a929e> in <module>
      7     title = Text()
      8
----> 9 Post().to_dict(include_meta=True)

/usr/local/lib/python3.6/site-packages/elasticsearch_dsl/document.py in to_dict(self, include_meta, skip_empty)                                                                                                     
    309
    310         # in case of to_dict include the index unlike save/update/delete
--> 311         index = self._get_index(required=False)
    312         if index is not None:
    313             meta['_index'] = index

/usr/local/lib/python3.6/site-packages/elasticsearch_dsl/document.py in _get_index(self, index, required)
    146             raise ValidationException('No index')
    147         if index and '*' in index:
--> 148             raise ValidationException('You cannot write to a wildcard index.')
    149         return index
    150

ValidationException: You cannot write to a wildcard index.

Index.document() is documented here.