--- a/Lib/test/test_raise.py	Sat Jan 28 20:33:52 2012 -0500
+++ b/Lib/test/test_raise.py	Tue Jan 31 23:14:15 2012 -0800
@@ -77,6 +77,16 @@ class TestRaise(unittest.TestCase):
                 nested_reraise()
         self.assertRaises(TypeError, reraise)
 
+    def test_raise_from_None(self):
+        try:
+            try:
+                raise TypeError("foo")
+            except:
+                raise ValueError() from None
+        except ValueError as e:
+            self.assertTrue(isinstance(e.__context__, TypeError))
+            self.assertIsNone(e.__cause__)
+
     def test_with_reraise1(self):
         def reraise():
             try: