LookupError: unknown encoding

[MattiaFailla]

Hi, I'm getting this error while getting information from a mail: I'm on Python3.6

Traceback (most recent call last):
  File "/home/mattia/.local/lib/python3.6/site-packages/imbox/parser.py", line 128, in decode_content
    return content.decode(charset, 'ignore')
LookupError: unknown encoding: 

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "app.py", line 687, in <module>
    download_every_email()
  File "app.py", line 668, in download_every_email
    for uid, message in reversed(all_inbox_messages):
  File "/home/mattia/.local/lib/python3.6/site-packages/imbox/messages.py", line 61, in __getitem__
    return uid, self._fetch_email(uid)
  File "/home/mattia/.local/lib/python3.6/site-packages/imbox/messages.py", line 28, in _fetch_email
    parser_policy=self.parser_policy)
  File "/home/mattia/.local/lib/python3.6/site-packages/imbox/parser.py", line 141, in fetch_email_by_uid
    email_object = parse_email(raw_email, policy=parser_policy)
  File "/home/mattia/.local/lib/python3.6/site-packages/imbox/parser.py", line 187, in parse_email
    content = decode_content(part)
  File "/home/mattia/.local/lib/python3.6/site-packages/imbox/parser.py", line 130, in decode_content
    return content.decode(charset.replace("-", ""), 'ignore')
LookupError: unknown encoding: