Django sequence field is creating two instances of SequenceField

[luanfonceca]

I am having a weird error, i installed the package, setup the settings, run the migrate, in one of my models i created a field:

...

class Order(models.Model):
    number = SequenceField(
        key='order.sequence.1', template='%b%NNNN', auto=True)

When i ran the makemigrations i get the following error: SequenceFieldException: The key parameter is mandatory and is missing. Digging into that i put an pdb on the SequenceField __init__ function. The first time the pdb was called it is on my number field, but there is someone else instantiating this Field and in the next time i am getting that error.

I am using the django 1.8.4