choices issue

== App model ==
class Target(Document):
    Age = IntField()
    Gender = StringField(max_length=1,choices=(('M','Male'),('F','Female')))
    Videos = SortedListField(EmbeddedDocumentField(ContentRating))


==Django shell ==

t=Target(Age=24,Gender='M')
t.Videos.append(cr)
t.save()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python2.6/dist-packages/mongoengine-0.4-py2.6.egg/mongoengine/document.py", line 73, in save
    self.validate()
  File "/usr/local/lib/python2.6/dist-packages/mongoengine-0.4-py2.6.egg/mongoengine/base.py", line 357, in validate
    field._validate(value)
  File "/usr/local/lib/python2.6/dist-packages/mongoengine-0.4-py2.6.egg/mongoengine/base.py", line 92, in _validate
    % unicode(self.choices))
ValidationError: Value must be one of (('M', 'Male'), ('F', 'Female')).