diff -r 284b3de802b7 Lib/test/test_capi.py
--- a/Lib/test/test_capi.py	Sat Jan 30 04:45:02 2016 +0000
+++ b/Lib/test/test_capi.py	Fri Jan 29 13:08:15 2016 +0200
@@ -236,6 +236,20 @@ class CAPITest(unittest.TestCase):
                              'return_result_with_error.* '
                              'returned a result with an error set')
 
+    def test_buildvalue_N(self):
+        getrefcount = support.get_attribute(sys, 'getrefcount')
+        obj = object()
+        cnt = getrefcount(obj)
+        res = _testcapi.buildvalue_cN(65, obj)
+        self.assertIs(res[1], obj)
+        self.assertEqual(getrefcount(obj), cnt + 1)
+        # test that the 'N' argument is decrefed in case of error
+        obj = object()
+        cnt = getrefcount(obj)
+        with self.assertRaises((OverflowError, ValueError)):
+            res = _testcapi.buildvalue_cN(2**32, obj)
+        self.assertEqual(getrefcount(obj), cnt)
+
 
 @unittest.skipUnless(threading, 'Threading required for this test.')
 class TestPendingCalls(unittest.TestCase):
diff -r 284b3de802b7 Modules/_testcapimodule.c
--- a/Modules/_testcapimodule.c	Sat Jan 30 04:45:02 2016 +0000
+++ b/Modules/_testcapimodule.c	Fri Jan 29 13:08:15 2016 +0200
@@ -872,6 +872,18 @@ test_L_code(PyObject *self)
 
 #endif  /* ifdef HAVE_LONG_LONG */
 
+static PyObject *
+buildvalue_cN(PyObject *self, PyObject *args)
+{
+    int i;
+    PyObject *o;
+    if (!PyArg_ParseTuple(args, "iO", &i, &o))
+        return NULL;
+    Py_INCREF(o);
+    return Py_BuildValue("cN", i, o);
+}
+
+
 /* Test tuple argument processing */
 static PyObject *
 getargs_tuple(PyObject *self, PyObject *args)
@@ -3653,6 +3665,7 @@ static PyMethodDef TestMethods[] = {
     {"test_pep3118_obsolete_write_locks", (PyCFunction)test_pep3118_obsolete_write_locks, METH_NOARGS},
 #endif
     {"getbuffer_with_null_view", getbuffer_with_null_view, METH_O},
+    {"buildvalue_cN",           buildvalue_cN,                   METH_VARARGS},
     {"getargs_tuple",           getargs_tuple,                   METH_VARARGS},
     {"getargs_keywords", (PyCFunction)getargs_keywords,
       METH_VARARGS|METH_KEYWORDS},
diff -r 284b3de802b7 Python/modsupport.c
--- a/Python/modsupport.c	Sat Jan 30 04:45:02 2016 +0000
+++ b/Python/modsupport.c	Fri Jan 29 13:08:15 2016 +0200
@@ -156,10 +156,11 @@ do_mktuple(const char **p_format, va_lis
     int itemfailed = 0;
     if (n < 0)
         return NULL;
-    if ((v = PyTuple_New(n)) == NULL)
-        return NULL;
     /* Note that we can't bail immediately on error as this will leak
        refcounts on any 'N' arguments. */
+    if ((v = PyTuple_New(n)) == NULL) {
+        itemfailed = 1;
+    }
     for (i = 0; i < n; i++) {
         PyObject *w;
 
@@ -168,20 +169,19 @@ do_mktuple(const char **p_format, va_lis
             PyErr_Fetch(&exception, &value, &tb);
             w = do_mkvalue(p_format, p_va, flags);
             PyErr_Restore(exception, value, tb);
+            Py_XDECREF(w);
         }
         else {
             w = do_mkvalue(p_format, p_va, flags);
+            if (w == NULL) {
+                itemfailed = 1;
+            }
+            PyTuple_SET_ITEM(v, i, w);
         }
-        if (w == NULL) {
-            itemfailed = 1;
-            Py_INCREF(Py_None);
-            w = Py_None;
-        }
-        PyTuple_SET_ITEM(v, i, w);
     }
     if (itemfailed) {
         /* do_mkvalue() should have already set an error */
-        Py_DECREF(v);
+        Py_XDECREF(v);
         return NULL;
     }
     if (**p_format != endchar) {