diff -r fe532dccf8f6 Lib/test/test_winreg.py
--- a/Lib/test/test_winreg.py	Mon Apr 14 10:30:43 2014 -0400
+++ b/Lib/test/test_winreg.py	Mon Apr 14 14:59:33 2014 -0400
@@ -354,6 +354,20 @@
         finally:
             DeleteKey(HKEY_CURRENT_USER, test_key_name)
 
+    def test_setvalueex_crash_with_none_arg(self):
+        # Test for Issue #21151, segfault when None is passed to SetValueEx
+        try:
+            with CreateKey(HKEY_CURRENT_USER, test_key_name) as ck:
+                self.assertNotEqual(ck.handle, 0)
+                test_val = None
+                SetValueEx(ck, "test_name", 0, REG_BINARY, test_val)
+                ret_val, ret_type = QueryValueEx(ck, "test_name")
+                self.assertEqual(ret_type, REG_BINARY)
+                self.assertEqual(ret_val, test_val)
+        finally:
+            DeleteKey(HKEY_CURRENT_USER, test_key_name)
+        
+
 
 
 @unittest.skipUnless(REMOTE_NAME, "Skipping remote registry tests")
diff -r fe532dccf8f6 PC/winreg.c
--- a/PC/winreg.c	Mon Apr 14 10:30:43 2014 -0400
+++ b/PC/winreg.c	Mon Apr 14 14:59:33 2014 -0400
@@ -871,8 +871,10 @@
         /* ALSO handle ALL unknown data types here.  Even if we can't
            support it natively, we should handle the bits. */
         default:
-            if (value == Py_None)
+            if (value == Py_None) {
                 *retDataSize = 0;
+                *retDataBuf = NULL;
+            }
             else {
                 Py_buffer view;