diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 7e119c2f86..67acbbae76 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -510,8 +510,8 @@ class AutoField(Field):
         'invalid': _(u"'%s' value must be an integer."),
     }
     def __init__(self, *args, **kwargs):
-        assert (kwargs.get('primary_key', False) is True,
-                "%ss must have primary_key=True." % self.__class__.__name__)
+        assert kwargs.get('primary_key', False) is True, \
+               "%ss must have primary_key=True." % self.__class__.__name__
         kwargs['blank'] = True
         Field.__init__(self, *args, **kwargs)
 
@@ -536,8 +536,8 @@ class AutoField(Field):
         return int(value)
 
     def contribute_to_class(self, cls, name):
-        assert (not cls._meta.has_auto_field,
-                "A model can't have more than one AutoField.")
+        assert not cls._meta.has_auto_field, \
+               "A model can't have more than one AutoField."
         super(AutoField, self).contribute_to_class(cls, name)
         cls._meta.has_auto_field = True
         cls._meta.auto_field = self
diff --git a/tests/modeltests/validation/models.py b/tests/modeltests/validation/models.py
index fca2cef261..182e739daf 100644
--- a/tests/modeltests/validation/models.py
+++ b/tests/modeltests/validation/models.py
@@ -90,3 +90,13 @@ class GenericIPAddressTestModel(models.Model):
 
 class GenericIPAddrUnpackUniqueTest(models.Model):
     generic_v4unpack_ip = models.GenericIPAddressField(blank=True, unique=True, unpack_ipv4=True)
+
+
+try:
+    # A model can't have multiple AutoFields
+    # Refs #12467.
+    class MultipleAutoFields(models.Model):
+        auto1 = models.AutoField(primary_key=True)
+        auto2 = models.AutoField(primary_key=True)
+except AssertionError, e:
+    assert e.message == u"A model can't have more than one AutoField."
\ No newline at end of file
diff --git a/tests/modeltests/validation/test_error_messages.py b/tests/modeltests/validation/test_error_messages.py
index 43b707e632..299a93a41a 100644
--- a/tests/modeltests/validation/test_error_messages.py
+++ b/tests/modeltests/validation/test_error_messages.py
@@ -12,6 +12,12 @@ class ValidationMessagesTest(TestCase):
             f.clean('foo', None)
         except ValidationError, e:
             self.assertEqual(e.messages, [u"'foo' value must be an integer."])
+        # primary_key must be True. Refs #12467.
+        self.assertRaises(AssertionError, models.AutoField, 'primary_key', False)
+        try:
+            models.AutoField(primary_key=False)
+        except AssertionError, e:
+            self.assertEqual(e.message, u"AutoFields must have primary_key=True.")
 
     def test_integer_field_raises_error_message(self):
         f = models.IntegerField()