model field choices are not enforced

[stiffupperlip]

In Django 1.8.8 when I create a model class like below, choices are not enforced when creating an instance of the model class:

class HTTPMethod(models.Model):

HTTP_METHODS = [(_, _) for _ in ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace', 'connect']]

id = models.AutoField(primary_key=True)
name = models.CharField(choices=HTTP_METHODS, unique=True, max_length=255)

h = HTTPMethod(name='something invalid')
h.save()

No errors are raised.

Python 2.7.6 on Ubuntu 14.04