diff --git a/django/contrib/auth/models.py b/django/contrib/auth/models.py
index 87c3adf..49bdb32 100644
--- a/django/contrib/auth/models.py
+++ b/django/contrib/auth/models.py
@@ -144,9 +144,8 @@ class UserManager(BaseUserManager):
         """
         if not username:
             raise ValueError('The given username must be set')
-        email = self.normalize_email(email)
-        username = self.normalize_username(username)
         user = self.model(username=username, email=email, **extra_fields)
+        user.clean()
         user.set_password(password)
         user.save(using=self._db)
         return user
@@ -344,6 +343,11 @@ class AbstractUser(AbstractBaseUser, PermissionsMixin):
         verbose_name_plural = _('users')
         abstract = True

+    def clean(self):
+        super(AbstractUser, self).clean()
+        self.email = self.__class__.objects.normalize_email(self.email)
+        self.username = self.__class__.objects.normalize_username(self.username)
+
     def get_full_name(self):
         """
         Returns the first_name plus the last_name, with a space in between.
diff --git a/tests/auth_tests/test_forms.py b/tests/auth_tests/test_forms.py
index d2ce828..6b3aac2 100644
--- a/tests/auth_tests/test_forms.py
+++ b/tests/auth_tests/test_forms.py
@@ -129,13 +129,17 @@ class UserCreationFormTest(TestDataMixin, TestCase):
         omega_username = 'iamtheΩ'  # U+03A9 GREEK CAPITAL LETTER OMEGA
         ohm_username = 'iamtheΩ'  # U+2126 OHM SIGN
         self.assertNotEqual(omega_username, ohm_username)
-        User.objects.create_user(username=omega_username, password='pwd')
         data = {
-            'username': ohm_username,
+            'username': omega_username,
             'password1': 'pwd2',
             'password2': 'pwd2',
         }
         form = UserCreationForm(data)
+        self.assertTrue(form.is_valid())
+        form.save()
+
+        data['username'] = ohm_username
+        form = UserCreationForm(data)
         self.assertFalse(form.is_valid())
         self.assertEqual(
             form.errors['username'], ["A user with that username already exists."]