Can't serialize select result with fields from two tables

Traceback (most recent call last):
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/restricted.py", line 188, in restricted
    exec ccode in environment
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/applications/Hotelaria/controllers/despesa.py", line 81, in <module>
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/globals.py", line 95, in <lambda>
    self._caller = lambda f: f()
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/applications/Hotelaria/controllers/despesa.py", line 50, in getDespesasPorHospedagem
    return response.json({'despesas': despesas})
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/globals.py", line 206, in json
    return json(data)
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/serializers.py", line 31, in json
    return simplejson.dumps(value)
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/contrib/simplejson/__init__.py", line 228, in dumps
    return _default_encoder.encode(obj)
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/contrib/simplejson/encoder.py", line 232, in encode
    chunks = list(chunks)
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/contrib/simplejson/encoder.py", line 501, in _iterencode
    for chunk in _iterencode_dict(o, _current_indent_level):
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/contrib/simplejson/encoder.py", line 475, in _iterencode_dict
    for chunk in chunks:
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/contrib/simplejson/encoder.py", line 511, in _iterencode
    o = _default(o)
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/contrib/simplejson/encoder.py", line 205, in default
    return o.as_dict()
  File "/media/dadosext/Rafael/Projetos-Programacao/Python/web2py/gluon/dal.py", line 4832, in as_dict
    return dict([(r[key],r) for r in rows])
KeyError: 'id'