gistfile1.diff

diff --git a/django/db/models/query.py b/django/db/models/query.py
index a3e0a95..84434df 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -149,10 +149,14 @@ class QuerySet(object):
         """
         if not isinstance(k, (slice,) + six.integer_types):
             raise TypeError
-        assert ((not isinstance(k, slice) and (k >= 0))
-                or (isinstance(k, slice) and (k.start is None or k.start >= 0)
-                    and (k.stop is None or k.stop >= 0))), \
-                "Negative indexing is not supported."
+
+        assert (
+            not isinstance(k, slice) or (
+                isinstance(k, slice) and
+                (k.start is None or k.start >= 0) and
+                (k.stop is None or k.stop >= 0)
+            )
+        ), "Negative indexing is not supported."
 
         if self._result_cache is not None:
             return self._result_cache[k]
@@ -170,8 +174,13 @@ class QuerySet(object):
             qs.query.set_limits(start, stop)
             return list(qs)[::k.step] if k.step else qs
 
-        qs = self._clone()
-        qs.query.set_limits(k, k + 1)
+        if k >= 0:
+            qs = self._clone()
+            qs.query.set_limits(k, k + 1)
+        else:
+            k *= -1
+            qs = self.reverse() if self.ordered else self.order_by('-pk')
+            qs.query.set_limits(k - 1, k)
         return list(qs)[0]
 
     def __and__(self, other):
diff --git a/tests/basic/tests.py b/tests/basic/tests.py
index 55ed6a4..812e19b 100644
--- a/tests/basic/tests.py
+++ b/tests/basic/tests.py
@@ -440,15 +440,8 @@ class ModelTest(TestCase):
         except Exception as e:
             self.fail('Should raise an AssertionError, not %s' % e)
 
-        # Negative slices are not supported, due to database constraints.
-        # (hint: inverting your ordering might do what you need).
-        try:
-            Article.objects.all()[-1]
-            self.fail('Should raise an AssertionError')
-        except AssertionError as e:
-            self.assertEqual(str(e), "Negative indexing is not supported.")
-        except Exception as e:
-            self.fail('Should raise an AssertionError, not %s' % e)
+        # Test negative indexing.
+        self.assertEqual(Article.objects.all()[-3], a4)
 
         error = None
         try: