diff --git a/django/forms/models.py b/django/forms/models.py
index 4e8578e55e..1cbfba9602 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -214,6 +214,8 @@ class BaseModelForm(BaseForm):
                  empty_permitted=False, instance=None):
         opts = self._meta
         if instance is None:
+            if opts.model is None:
+                raise ValueError('ModelForm has no model class specified.')
             # if we didn't get an instance, instantiate a new one
             self.instance = opts.model()
             object_data = {}
diff --git a/tests/regressiontests/model_forms_regress/tests.py b/tests/regressiontests/model_forms_regress/tests.py
index 85e284b639..862c39c8d4 100644
--- a/tests/regressiontests/model_forms_regress/tests.py
+++ b/tests/regressiontests/model_forms_regress/tests.py
@@ -100,4 +100,10 @@ class CustomFieldSaveTests(TestCase):
         # It's enough that the form saves without error -- the custom save routine will
         # generate an AssertionError if it is called more than once during save.
         form = CFFForm(data = {'f': None})
-        form.save()
\ No newline at end of file
+        form.save()
+
+class ModelClassTests(TestCase):
+    def test_no_model_class(self):
+        class NoModelModelForm(forms.ModelForm):
+            pass
+        self.assertRaises(ValueError, NoModelModelForm)