ManyToManyField shows up last in admin form & model form

[Andreas]

I have a model that contains a ManyToManyField. Independent of where in the model definition I put this ManyToManyField, it's always shown last in the admin edit / new page, as well as in my custom forms.
If I change the field definition from ManyToManyField to ForeignKey, the position of this field is where I expect it to be (in this example, after the project field).

class Experiment(models.Model):
    author          = models.ForeignKey(User)
    title           = models.CharField(max_length=255)
    slug            = models.SlugField()
    project         = models.ForeignKey(Project)
    protocol        = models.ManyToManyField(Protocol, blank=True, null=True)
    plan            = models.TextField(blank=True, null=True)
    end_date        = models.DateField(blank=True, null=True)

[Alex Gaynor]

This is a duplicate of #6953.