diff -r 5358ee70f831 Lib/test/test_descr.py
--- a/Lib/test/test_descr.py	Sat Apr 13 17:46:04 2013 +0100
+++ b/Lib/test/test_descr.py	Sat Apr 13 21:01:52 2013 +0100
@@ -1784,6 +1784,7 @@
             ("__exit__", run_context, swallow, set(), {"__enter__" : iden}),
             ("__complex__", complex, complex_num, set(), {}),
             ("__format__", format, format_impl, set(), {}),
+            ("__round__", round, zero, set(), {}),
             ("__floor__", math.floor, zero, set(), {}),
             ("__trunc__", math.trunc, zero, set(), {}),
             ("__trunc__", int, zero, set(), {}),
diff -r 5358ee70f831 Python/bltinmodule.c
--- a/Python/bltinmodule.c	Sat Apr 13 17:46:04 2013 +0100
+++ b/Python/bltinmodule.c	Sat Apr 13 21:01:52 2013 +0100
@@ -1810,10 +1810,10 @@
 static PyObject *
 builtin_round(PyObject *self, PyObject *args, PyObject *kwds)
 {
-    static PyObject *round_str = NULL;
     PyObject *ndigits = NULL;
     static char *kwlist[] = {"number", "ndigits", 0};
     PyObject *number, *round;
+    _Py_IDENTIFIER(__round__);
 
     if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:round",
                                      kwlist, &number, &ndigits))
@@ -1824,24 +1824,20 @@
             return NULL;
     }
 
-    if (round_str == NULL) {
-        round_str = PyUnicode_InternFromString("__round__");
-        if (round_str == NULL)
-            return NULL;
-    }
-
-    round = _PyType_Lookup(Py_TYPE(number), round_str);
+    round = _PyObject_LookupSpecial(number, &PyId___round__);
     if (round == NULL) {
-        PyErr_Format(PyExc_TypeError,
-                     "type %.100s doesn't define __round__ method",
-                     Py_TYPE(number)->tp_name);
+        if (!PyErr_Occurred()) {
+            PyErr_Format(PyExc_TypeError,
+                         "type %.100s doesn't define __round__ method",
+                         Py_TYPE(number)->tp_name);
+        }
         return NULL;
     }
 
     if (ndigits == NULL)
-        return PyObject_CallFunction(round, "O", number);
+        return PyObject_CallObject(round, NULL);
     else
-        return PyObject_CallFunction(round, "OO", number, ndigits);
+        return PyObject_CallFunctionObjArgs(round, ndigits, NULL);
 }
 
 PyDoc_STRVAR(round_doc,