diff -r c91e7f707562 Python/ceval.c
--- a/Python/ceval.c	Tue Jul 09 00:49:03 2013 +0200
+++ b/Python/ceval.c	Tue Jul 09 01:57:45 2013 +0200
@@ -3821,8 +3821,12 @@ call_exc_trace(Py_tracefunc func, PyObje
     int err;
     PyErr_Fetch(&type, &value, &traceback);
     if (value == NULL) {
+        Py_INCREF(Py_None);
         value = Py_None;
-        Py_INCREF(value);
+    }
+    if (traceback == NULL) {
+        Py_INCREF(Py_None);
+        traceback = Py_None;
     }
     PyErr_NormalizeException(&type, &value, &traceback);
     arg = PyTuple_Pack(3, type, value, traceback);