diff -r 6b189f29b1e6 Lib/test/test_functools.py
--- a/Lib/test/test_functools.py	Wed Jun 05 18:37:50 2013 -0400
+++ b/Lib/test/test_functools.py	Thu Jun 06 23:12:33 2013 +0800
@@ -868,15 +868,22 @@
         @functools.singledispatch
         def g(obj):
             return "base"
-        class C:
+        class A:
             pass
-        class D(C):
+        class B:
             pass
-        def g_C(c):
-            return "C"
-        g.register(C, g_C)
-        self.assertEqual(g(C()), "C")
-        self.assertEqual(g(D()), "C")
+        class C(A):
+            pass
+        class D(C, B):
+            pass
+        def g_B(b):
+            return "B"
+        def g_A(a):
+            return "A"
+        g.register(B, g_B)
+        g.register(A, g_A)
+        #self.assertEqual(g(D()), "B") # I thought we check the class from left to right before going up
+        self.assertEqual(g(D()), "A")
 
     def test_classic_classes(self):
         @functools.singledispatch