1 files changed, 18 insertions, 0 deletions
diff --git a/tests/forms_tests/tests/test_extra.py b/tests/forms_tests/tests/test_extra.py
index afdfaf5281..ba835495c6 100644
--- a/tests/forms_tests/tests/test_extra.py
+++ b/tests/forms_tests/tests/test_extra.py
@@ -620,6 +620,24 @@ class FormsExtraTestCase(TestCase, AssertFormErrorsMixin):
         self.assertTrue(f.is_valid())
         self.assertEqual(f.cleaned_data['username'], 'sirrobin')
 
+    def test_changing_cleaned_data_in_clean(self):
+        class UserForm(Form):
+            username = CharField(max_length=10)
+            password = CharField(widget=PasswordInput)
+
+            def clean(self):
+                data = self.cleaned_data
+
+                # Return a different dict. We have not changed self.cleaned_data.
+                return {
+                    'username': data['username'].lower(),
+                    'password': 'this_is_not_a_secret',
+                }
+
+        f = UserForm({'username': 'SirRobin', 'password': 'blue'})
+        self.assertTrue(f.is_valid())
+        self.assertEqual(f.cleaned_data['username'], 'sirrobin')
+
     def test_overriding_errorlist(self):
         @python_2_unicode_compatible
         class DivErrorList(ErrorList):