Index: Lib/ctypes/test/test_parameters.py
===================================================================
--- Lib/ctypes/test/test_parameters.py	(revision 67679)
+++ Lib/ctypes/test/test_parameters.py	(working copy)
@@ -97,7 +97,7 @@
         self.failUnlessEqual(x.contents.value, 42)
         self.failUnlessEqual(LPINT(c_int(42)).contents.value, 42)
 
-        self.failUnlessEqual(LPINT.from_param(None), 0)
+        self.failUnlessEqual(LPINT.from_param(None), None)
 
         if c_int != c_long:
             self.assertRaises(TypeError, LPINT.from_param, pointer(c_long(42)))
Index: Modules/_ctypes/callproc.c
===================================================================
--- Modules/_ctypes/callproc.c	(revision 67679)
+++ Modules/_ctypes/callproc.c	(working copy)
@@ -546,6 +546,7 @@
  * C function call.
  *
  * 1. Python integers are converted to C int and passed by value.
+ *    Py_None is converted to a C NULL pointer.
  *
  * 2. 3-tuples are expected to have a format character in the first
  *    item, which must be 'i', 'f', 'd', 'q', or 'P'.
Index: Modules/_ctypes/_ctypes.c
===================================================================
--- Modules/_ctypes/_ctypes.c	(revision 67679)
+++ Modules/_ctypes/_ctypes.c	(working copy)
@@ -972,7 +972,7 @@
 	StgDictObject *typedict;
 
 	if (value == Py_None)
-		return PyInt_FromLong(0); /* NULL pointer */
+		return value; /* Let ConvParam convert to NULL pointer later */
 
 	typedict = PyType_stgdict(type);
 	assert(typedict); /* Cannot be NULL for pointer types */