diff --git a/django/db/models/query.py b/django/db/models/query.py
index c36a68f404..6a6fd82b18 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -303,6 +303,7 @@ class _QuerySet(object):
         assert self.query.can_filter(), \
                 "Cannot reorder a query once a slice has been taken."
         obj = self._clone()
+        obj.query.clear_ordering()
         obj.query.add_ordering(*field_names)
         return obj
 
diff --git a/tests/modeltests/ordering/models.py b/tests/modeltests/ordering/models.py
index 3e651d4ee7..d3eb7f0dc0 100644
--- a/tests/modeltests/ordering/models.py
+++ b/tests/modeltests/ordering/models.py
@@ -64,4 +64,11 @@ __test__ = {'API_TESTS':"""
 # don't know what order the output will be in.
 >>> Article.objects.order_by('?')
 [...]
+
+# order_by() overrides any previous ordering, so only the last one has any
+# effect.
+>>> Article.objects.order_by('id')
+[<Article: Article 1>, <Article: Article 2>, <Article: Article 3>, <Article: Article 4>]
+>>> Article.objects.order_by('id').order_by('-headline')
+[<Article: Article 4>, <Article: Article 3>, <Article: Article 2>, <Article: Article 1>]
 """}