diff -r bba20ce29d26 Lib/pprint.py
--- a/Lib/pprint.py	Wed Jul 18 15:12:47 2012 -0700
+++ b/Lib/pprint.py	Thu Jul 19 02:17:03 2012 +0300
@@ -86,7 +86,7 @@
         self.obj = obj
 
     def __lt__(self, other):
-        rv = self.obj.__lt__(other.obj)
+        rv = type(self.obj).__lt__(self.obj, other.obj)
         if rv is NotImplemented:
             rv = (str(type(self.obj)), id(self.obj)) < \
                  (str(type(other.obj)), id(other.obj))
diff -r bba20ce29d26 Lib/test/test_pprint.py
--- a/Lib/test/test_pprint.py	Wed Jul 18 15:12:47 2012 -0700
+++ b/Lib/test/test_pprint.py	Thu Jul 19 02:17:03 2012 +0300
@@ -32,6 +32,13 @@
     def __repr__(self):
         return str(id(self))
 
+class A:
+    pass
+
+class B:
+    pass
+
+
 class QueryTestCase(unittest.TestCase):
 
     def setUp(self):
@@ -451,6 +458,19 @@
         self.assertEqual(pprint.pformat(nested_dict, depth=1), lv1_dict)
         self.assertEqual(pprint.pformat(nested_list, depth=1), lv1_list)
 
+    def test_class_keys(self):
+        # Issue 10017
+        dict_with_classes = {A: 1, B: 2}
+        # Class objects fall back to sorting by id
+        classes = map(repr, sorted([A, B], key=id))
+        classes_expected = '{{{0}: 1, {1}: 2}}'.format(*classes)
+
+        dict_with_class = {'key1': 1, A: 2, 'key2': 3}
+        class_expected = "{{'key1': 1, 'key2': 3, {A}: 2}}".format(A=repr(A))
+
+        self.assertEqual(pprint.pformat(dict_with_classes), classes_expected)
+        self.assertEqual(pprint.pformat(dict_with_class), class_expected)
+
     def test_sort_unorderable_values(self):
         # Issue 3976:  sorted pprints fail for unorderable values.
         n = 20