diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 42c36a6..f92b1e4 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -331,13 +331,20 @@
    :func:`setrecursionlimit`.
 
 
-.. function:: getsizeof(object)
+.. function:: getsizeof(object[, default])
 
    Return the size of an object in bytes. The object can be any type of
    object. All built-in objects will return correct results, but this
-   does not have to hold true for third-party extensions as it is implementation 
+   does not have to hold true for third-party extensions as it is implementation
    specific.
 
+   The *default* argument allows to define a value which will be returned
+   if the object type does not provide means to retrieve the size and would
+   cause a `TypeError`. 
+
+   func:`getsizeof` calls the object's __sizeof__ method and adds an additional
+   garbage collector overhead if the object is managed by the garbage collector.
+
    .. versionadded:: 2.6
 
 
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 07db156..cd8f565 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -373,6 +373,9 @@
 
 class SizeofTest(unittest.TestCase):
 
+    TPFLAGS_HAVE_GC = 1<<14
+    TPFLAGS_HEAPTYPE = 1<<9
+
     def setUp(self):
         self.c = len(struct.pack('c', ' '))
         self.H = len(struct.pack('H', 0))
@@ -382,22 +385,27 @@
         # due to missing size_t information from struct, it is assumed that
         # sizeof(Py_ssize_t) = sizeof(void*)
         self.header = 'PP'
+        self.vheader = self.header + 'P'
         if hasattr(sys, "gettotalrefcount"):
             self.header += '2P'
+            self.vheader += '2P'
+        import _testcapi
+        self.gc_headsize = _testcapi.SIZEOF_PYGC_HEAD
         self.file = open(test.support.TESTFN, 'wb')
 
     def tearDown(self):
         self.file.close()
         test.support.unlink(test.support.TESTFN)
 
-    def check_sizeof(self, o, size, size2=None):
-        """Check size of o. Possible are size and optionally size2)."""
+    def check_sizeof(self, o, size):
         result = sys.getsizeof(o)
-        msg = 'wrong size for %s: got %d, expected ' % (type(o), result)
-        if (size2 != None) and (result != size):
-            self.assertEqual(result, size2, msg + str(size2))
-        else:
-            self.assertEqual(result, size, msg + str(size))
+        # add GC header size
+        if ((type(o) == type) and (o.__flags__ & self.TPFLAGS_HEAPTYPE) or\
+           ((type(o) != type) and (type(o).__flags__ & self.TPFLAGS_HAVE_GC))):
+            size += self.gc_headsize
+        msg = 'wrong size for %s: got %d, expected %d' \
+              % (type(o), result, size)
+        self.assertEqual(result, size, msg)
 
     def calcsize(self, fmt):
         """Wrapper around struct.calcsize which enforces the alignment of the
@@ -408,29 +416,116 @@
         """
         return struct.calcsize(fmt + '0P')
 
-    def test_standardtypes(self):
+    def test_gc_head_size(self):
+        # Check that the gc header size is added to objects tracked by the gc.
         h = self.header
+        vh = self.vheader
         size = self.calcsize
+        gc_header_size = self.gc_headsize
+        # bool objects are not gc tracked
+        self.assertEqual(sys.getsizeof(True), size(vh) + self.H)
+        # but lists are
+        self.assertEqual(sys.getsizeof([]), size(vh + 'PP') + gc_header_size)
+
+    def test_default(self):
+        h = self.header
+        vh = self.vheader
+        size = self.calcsize
+        self.assertEqual(sys.getsizeof(True), size(vh) + self.H)
+        self.assertEqual(sys.getsizeof(True, -1), size(vh) + self.H)
+
+    def test_objecttypes(self):
+        # check all types defined in Objects/
+        h = self.header
+        vh = self.vheader
+        size = self.calcsize
+        check = self.check_sizeof
+        # bool
+        check(True, size(vh) + self.H)
+        # buffer
+        # XXX
+        # builtin_function_or_method
+        check(len, size(h + '3P'))
+        # bytearray
+        samples = [b'', b'u'*100000]
+        for sample in samples:
+            x = bytearray(sample)
+            check(x, size(vh + 'iPP') + x.__alloc__() * self.c)
+        # bytearray_iterator
+        check(iter(bytearray()), size(h + 'PP'))
         # cell
         def get_cell():
             x = 42
             def inner():
                 return x
             return inner
-        self.check_sizeof(get_cell().__closure__[0], size(h + 'P'))
+        check(get_cell().__closure__[0], size(h + 'P'))
         # code
-        self.check_sizeof(get_cell().__code__, size(h + '5i8Pi2P'))
+        check(get_cell().__code__, size(h + '5i8Pi2P'))
         # complex
-        self.check_sizeof(complex(0,1), size(h + '2d'))
+        check(complex(0,1), size(h + '2d'))
+        # method_descriptor (descriptor object)
+        check(str.lower, size(h + '2PP'))
+        # classmethod_descriptor (descriptor object)
+        # XXX
+        # member_descriptor (descriptor object)
+        import datetime
+        check(datetime.timedelta.days, size(h + '2PP'))
+        # getset_descriptor (descriptor object)
+        import collections
+        check(collections.defaultdict.default_factory, size(h + '2PP'))
+        # wrapper_descriptor (descriptor object)
+        check(int.__add__, size(h + '2P2P'))
+        # method-wrapper (descriptor object)
+        check({}.__iter__, size(h + '2P'))
+        # dict
+        check({}, size(h + '3P2P' + 8*'P2P'))
+        longdict = {1:1, 2:2, 3:3, 4:4, 5:5, 6:6, 7:7, 8:8}
+        check(longdict, size(h + '3P2P' + 8*'P2P') + 16*size('P2P'))
+        # dictionary-keyiterator
+        check({}.keys(), size(h + 'P'))
+        # dictionary-valueiterator
+        check({}.values(), size(h + 'P'))
+        # dictionary-itemiterator
+        check({}.items(), size(h + 'P'))
+        # dictproxy
+        class C(object): pass
+        check(C.__dict__, size(h + 'P'))
+        # BaseException
+        check(BaseException(), size(h + '5P'))
+        # UnicodeEncodeError
+        check(UnicodeEncodeError("", "", 0, 0, ""), size(h + '5P 2P2PP'))
+        # UnicodeDecodeError
+        # XXX
+#        check(UnicodeDecodeError("", "", 0, 0, ""), size(h + '5P2PP'))
+        # UnicodeTranslateError
+        check(UnicodeTranslateError("", 0, 1, ""), size(h + '5P 2P2PP'))
+        # ellipses
+        check(Ellipsis, size(h + ''))
+        # EncodingMap
+        import codecs, encodings.iso8859_3
+        x = codecs.charmap_build(encodings.iso8859_3.decoding_table)
+        check(x, size(h + '32B2iB'))
         # enumerate
-        self.check_sizeof(enumerate([]), size(h + 'l3P'))
+        check(enumerate([]), size(h + 'l3P'))
         # reverse
-        self.check_sizeof(reversed(''), size(h + 'PP'))
+        check(reversed(''), size(h + 'PP'))
         # float
-        self.check_sizeof(float(0), size(h + 'd'))
+        check(float(0), size(h + 'd'))
+        # sys.floatinfo
+        check(sys.float_info, size(vh) + self.P * len(sys.float_info))
+        # frame
+        import inspect
+        CO_MAXBLOCKS = 20
+        x = inspect.currentframe()
+        ncells = len(x.f_code.co_cellvars)
+        nfrees = len(x.f_code.co_freevars)
+        extras = x.f_code.co_stacksize + x.f_code.co_nlocals +\
+                  ncells + nfrees - 1
+        check(x, size(vh + '12P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
         # function
         def func(): pass
-        self.check_sizeof(func, size(h + '11P'))
+        check(func, size(h + '11P'))
         class c():
             @staticmethod
             def foo():
@@ -439,40 +534,99 @@
             def bar(cls):
                 pass
             # staticmethod
-            self.check_sizeof(foo, size(h + 'P'))
+            check(foo, size(h + 'P'))
             # classmethod
-            self.check_sizeof(bar, size(h + 'P'))
+            check(bar, size(h + 'P'))
         # generator
         def get_gen(): yield 1
-        self.check_sizeof(get_gen(), size(h + 'Pi2P'))
-        # builtin_function_or_method
-        self.check_sizeof(abs, size(h + '3P'))
+        check(get_gen(), size(h + 'Pi2P'))
+        # iterator
+        check(iter('abc'), size(h + 'lP'))
+        # callable-iterator
+        import re
+        check(re.finditer('',''), size(h + '2P'))
+        # list
+        samples = [[], [1,2,3], ['1', '2', '3']]
+        for sample in samples:
+            check(sample, size(vh + 'PP') + len(sample)*self.P)
+        # sortwrapper (list)
+        # XXX
+        # cmpwrapper (list)
+        # XXX
+        # listiterator (list)
+        check(iter([]), size(h + 'lP'))
+        # listreverseiterator (list)
+        check(reversed([]), size(h + 'lP'))
+        # long
+        check(0, size(vh))
+        check(1, size(vh) + self.H)
+        check(-1, size(vh) + self.H)
+        check(32768, size(vh) + 2*self.H)
+        check(32768*32768-1, size(vh) + 2*self.H)
+        check(32768*32768, size(vh) + 3*self.H)
+        # memory
+        check(memoryview(b''), size(h + 'P P2P2i5P'))
         # module
-        self.check_sizeof(unittest, size(h + '3P'))
+        check(unittest, size(h + '3P'))
+        # None
+        check(None, size(h + ''))
+        # NotImplementedType
+        check(NotImplemented, size(h))
+        # object
+        check(object(), size(h + ''))
+        # property (descriptor object)
+        class C(object):
+            def getx(self): return self.__x
+            def setx(self, value): self.__x = value
+            def delx(self): del self.__x
+            x = property(getx, setx, delx, "")
+            check(x, size(h + '4Pi'))
+        # PyCObject
+        # XXX
+        # rangeiterator
+        check(iter(range(1)), size(h + '4l'))
+        # reverse
+        check(reversed(''), size(h + 'PP'))
         # range
-        self.check_sizeof(range(1), size(h + '3P'))
+        check(range(1), size(h + '3P'))
+        check(range(66000), size(h + '3l'))
+        # set
+        # frozenset
+        PySet_MINSIZE = 8
+        samples = [[], range(10), range(50)]
+        s = size(h + '3P2P' + PySet_MINSIZE*'lP' + 'lP')
+        for sample in samples:
+            minused = len(sample)
+            if minused == 0: tmp = 1
+            # the computation of minused is actually a bit more complicated
+            # but this suffices for the sizeof test
+            minused = minused*2
+            newsize = PySet_MINSIZE
+            while newsize <= minused:
+                newsize = newsize << 1
+            if newsize <= 8:
+                check(set(sample), s)
+                check(frozenset(sample), s)
+            else:
+                check(set(sample), s + newsize*struct.calcsize('lP'))
+                check(frozenset(sample), s + newsize*struct.calcsize('lP'))
+        # setiterator
+        check(iter(set()), size(h + 'P3P'))
         # slice
-        self.check_sizeof(slice(0), size(h + '3P'))
-
-        h += 'P'
-        # bool
-        self.check_sizeof(True, size(h + 'H'))
-        # new-style class
-        class class_newstyle(object):
-            def method():
-                pass
-        # type (PyTypeObject + PyNumberMethods + PyMappingMethods +
-        #       PySequenceMethods + PyBufferProcs)
-        self.check_sizeof(class_newstyle, size(h + 'P2P15Pl4PP9PP11PI') +\
-                                          size('16Pi17P 3P 10P 2P 2P'))
-
-    def test_specialtypes(self):
-        h = self.header
-        size = self.calcsize
-        # dict
-        self.check_sizeof({}, size(h + '3P2P') + 8*size('P2P'))
-        longdict = {1:1, 2:2, 3:3, 4:4, 5:5, 6:6, 7:7, 8:8}
-        self.check_sizeof(longdict, size(h + '3P2P') + (8+16)*size('P2P'))
+        check(slice(0), size(h + '3P'))
+        # super
+        check(super(int), size(h + '3P'))
+        # tuple
+        check((), size(vh))
+        check((1,2,3), size(vh) + 3*self.P)
+        # type
+        # (PyTypeObject + PyNumberMethods + PyMappingMethods +
+        #  PySequenceMethods + PyBufferProcs)
+        s = size(vh + 'P2P15Pl4PP9PP11PI') + size('16Pi17P 3P 10P 2P 2P')
+        check(int, s)
+        # class
+        class newstyleclass(object): pass
+        check(newstyleclass, s)
         # unicode
         usize = len('\0'.encode('unicode-internal'))
         samples = ['', '1'*100]
@@ -480,31 +634,38 @@
         # has been cached
         for s in samples:
             basicsize =  size(h + 'PPliP') + usize * (len(s) + 1)
-            defenc = bytes(s, 'ascii')
-            self.check_sizeof(s, basicsize,
-                              size2=basicsize + sys.getsizeof(defenc))
-            # trigger caching encoded version as bytes object
-            try:
-                getattr(sys, s)
-            except AttributeError:
-                pass
-            finally:
-                self.check_sizeof(s, basicsize + sys.getsizeof(defenc))
+            check(s, basicsize)
+        # weakref
+        import weakref
+        check(weakref.ref(int), size(h + '2Pl2P'))
+        # weakproxy
+        # XXX
+        # weakcallableproxy
+        check(weakref.proxy(int), size(h + '2Pl2P'))
 
-        h += 'P'
-        # list
-        self.check_sizeof([], size(h + 'PP'))
-        self.check_sizeof([1, 2, 3], size(h + 'PP') + 3*self.P)
-        # long
-        self.check_sizeof(0, size(h + 'H'))
-        self.check_sizeof(1, size(h + 'H'))
-        self.check_sizeof(-1, size(h + 'H'))
-        self.check_sizeof(32768, size(h + 'H') + self.H)
-        self.check_sizeof(32768*32768-1, size(h + 'H') + self.H)
-        self.check_sizeof(32768*32768, size(h + 'H') + 2*self.H)
-        # tuple
-        self.check_sizeof((), size(h))
-        self.check_sizeof((1,2,3), size(h) + 3*self.P)
+    def test_pythontypes(self):
+        # check all types defined in Python/
+        h = self.header
+        vh = self.vheader
+        size = self.calcsize
+        check = self.check_sizeof
+        # _ast.AST
+        import _ast
+        check(_ast.AST(), size(h + ''))
+        # imp.NullImporter
+        import imp
+        check(imp.NullImporter(self.file.name), size(h + ''))
+        try:
+            raise TypeError
+        except TypeError:
+            tb = sys.exc_info()[2]
+            # traceback
+            if tb != None:
+                check(tb, size(h + '2P2i'))
+        # symtable entry
+        # XXX
+        # sys.flags
+        check(sys.flags, size(vh) + self.P * len(sys.flags))
 
 
 def test_main():
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 651fb20..d8bb835 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -1182,6 +1182,7 @@
 	PyModule_AddObject(m, "ULLONG_MAX", PyLong_FromUnsignedLongLong(PY_ULLONG_MAX));
 	PyModule_AddObject(m, "PY_SSIZE_T_MAX", PyLong_FromSsize_t(PY_SSIZE_T_MAX));
 	PyModule_AddObject(m, "PY_SSIZE_T_MIN", PyLong_FromSsize_t(PY_SSIZE_T_MIN));
+	PyModule_AddObject(m, "SIZEOF_PYGC_HEAD", PyLong_FromSsize_t(sizeof(PyGC_Head)));
 
 	TestError = PyErr_NewException("_testcapi.error", NULL, NULL);
 	Py_INCREF(TestError);
diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index f97c467..0dfd25b 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -3033,6 +3033,19 @@
     return Py_BuildValue("(O(Ns)N)", Py_TYPE(self), latin1, "latin-1", dict);
 }
 
+PyDoc_STRVAR(sizeof_doc,
+"B.__sizeof__() -> int\n\
+ \n\
+Returns the size of B in memory, in bytes");
+static PyObject *
+bytes_sizeof(PyByteArrayObject *self)
+{
+	Py_ssize_t res;
+
+	res = sizeof(PyByteArrayObject) + self->ob_alloc * sizeof(char);
+	return PyLong_FromSsize_t(res);
+}
+
 static PySequenceMethods bytes_as_sequence = {
     (lenfunc)bytes_length,              /* sq_length */
     (binaryfunc)PyByteArray_Concat,         /* sq_concat */
@@ -3061,6 +3074,7 @@
 bytes_methods[] = {
     {"__alloc__", (PyCFunction)bytes_alloc, METH_NOARGS, alloc_doc},
     {"__reduce__", (PyCFunction)bytes_reduce, METH_NOARGS, reduce_doc},
+    {"__sizeof__", (PyCFunction)bytes_sizeof, METH_NOARGS, sizeof_doc},
     {"append", (PyCFunction)bytes_append, METH_O, append__doc__},
     {"capitalize", (PyCFunction)stringlib_capitalize, METH_NOARGS,
      _Py_capitalize__doc__},
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 48fc2ca..035c2c5 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -513,6 +513,29 @@
 	}
 }
 
+static PyObject *
+frame_sizeof(PyFrameObject *f)
+{
+	Py_ssize_t res, extras, ncells, nfrees;
+
+	ncells = PyTuple_GET_SIZE(f->f_code->co_cellvars);
+	nfrees = PyTuple_GET_SIZE(f->f_code->co_freevars);
+	extras = f->f_code->co_stacksize + f->f_code->co_nlocals +
+		 ncells + nfrees;
+	// subtract one as it is already included in PyFrameObject
+	res = sizeof(PyFrameObject) + (extras-1) * sizeof(PyObject *);
+
+	return PyLong_FromSsize_t(res);
+}
+
+PyDoc_STRVAR(sizeof__doc__,
+"F.__sizeof__() -> size of F in memory, in bytes");
+
+static PyMethodDef frame_methods[] = {
+	{"__sizeof__",	(PyCFunction)frame_sizeof,	METH_NOARGS,
+	 sizeof__doc__},
+	{NULL,		NULL}	/* sentinel */
+};
 
 PyTypeObject PyFrame_Type = {
 	PyVarObject_HEAD_INIT(&PyType_Type, 0)
@@ -542,7 +565,7 @@
 	0,					/* tp_weaklistoffset */
 	0,					/* tp_iter */
 	0,					/* tp_iternext */
-	0,					/* tp_methods */
+	frame_methods,				/* tp_methods */
 	frame_memberlist,			/* tp_members */
 	frame_getsetlist,			/* tp_getset */
 	0,					/* tp_base */
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 2c684cb..6cea51a 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -3638,9 +3638,7 @@
 {
 	Py_ssize_t res;
 
-	res = sizeof(PyLongObject) + abs(Py_SIZE(v)) * sizeof(digit);
-        if (Py_SIZE(v) != 0)
-		res -=  sizeof(digit);
+	res = sizeof(PyVarObject) + abs(Py_SIZE(v))*sizeof(digit);
 	return PyLong_FromSsize_t(res);
 }
 
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 461fee6..79598f2 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1944,6 +1944,18 @@
 
 PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
 
+static PyObject *
+set_sizeof(PySetObject *so)
+{
+	Py_ssize_t res;
+
+	res = sizeof(PySetObject);
+	if (so->table != so->smalltable)
+		res = res + (so->mask + 1) * sizeof(setentry);
+	return PyLong_FromSsize_t(res);
+}
+
+PyDoc_STRVAR(sizeof_doc, "S.__sizeof__() -> size of S in memory, in bytes");
 static int
 set_init(PySetObject *self, PyObject *args, PyObject *kwds)
 {
@@ -2011,6 +2023,8 @@
 	 reduce_doc},
 	{"remove",	(PyCFunction)set_remove,	METH_O,
 	 remove_doc},
+	{"__sizeof__",	(PyCFunction)set_sizeof,	METH_NOARGS,
+	 sizeof_doc},
 	{"symmetric_difference",(PyCFunction)set_symmetric_difference,	METH_O,
 	 symmetric_difference_doc},
 	{"symmetric_difference_update",(PyCFunction)set_symmetric_difference_update,	METH_O,
@@ -2127,6 +2141,8 @@
 	 issuperset_doc},
 	{"__reduce__",	(PyCFunction)set_reduce,	METH_NOARGS,
 	 reduce_doc},
+	{"__sizeof__",	(PyCFunction)set_sizeof,	METH_NOARGS,
+	 sizeof_doc},
 	{"symmetric_difference",(PyCFunction)set_symmetric_difference,	METH_O,
 	 symmetric_difference_doc},
 	{"union",	(PyCFunction)set_union,		METH_VARARGS,
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 9dead63..b0b525a 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -8350,20 +8350,8 @@
 static PyObject *
 unicode__sizeof__(PyUnicodeObject *v)
 {
-    PyObject *res = NULL, *defsize = NULL;
-
-    res = PyLong_FromSsize_t(sizeof(PyUnicodeObject) +
-                             sizeof(Py_UNICODE) * (v->length + 1));
-    if (v->defenc) {
-        defsize = PyObject_CallMethod(v->defenc, "__sizeof__", NULL);
-        if (defsize == NULL) {
-            Py_DECREF(res);
-            return NULL;
-        }
-        res = PyNumber_Add(res, defsize);
-        Py_DECREF(defsize);
-    }
-    return res;
+    return PyLong_FromSsize_t(sizeof(PyUnicodeObject) +
+                              sizeof(Py_UNICODE) * (v->length + 1));
 }
 
 PyDoc_STRVAR(sizeof__doc__,
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 2a98eb5..e45d2a3 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -610,9 +610,16 @@
 #endif /* USE_MALLOPT */
 
 static PyObject *
-sys_getsizeof(PyObject *self, PyObject *args)
+sys_getsizeof(PyObject *self, PyObject *args, PyObject *kwds)
 {
-	static PyObject * str__sizeof__ = NULL;
+	PyObject *res = NULL;
+	static PyObject *str__sizeof__, *gc_head_size = NULL;
+	static char *kwlist[] = {"object", "default", 0};
+	PyObject *o, *dflt = NULL;
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:getsizeof",
+					 kwlist, &o, &dflt))
+		return NULL;
 
 	/* Initialize static variable needed by _PyType_Lookup */
 	if (str__sizeof__ == NULL) {
@@ -621,24 +628,47 @@
 			return NULL;
 	}
 
-	/* Type objects */
-	if (PyType_Check(args)){
-		PyObject *method = _PyType_Lookup(Py_TYPE(args),
-						  str__sizeof__);
-		if (method == NULL) {
-			PyErr_Format(PyExc_TypeError,
-				     "Type %.100s doesn't define __sizeof__",
-				     Py_TYPE(args)->tp_name);
+        /* Initialize static variable for GC head size */
+	if (gc_head_size == NULL) {
+		gc_head_size = PyLong_FromSsize_t(sizeof(PyGC_Head));
+		if (gc_head_size == NULL)
 			return NULL;
-		}
-		return PyObject_CallFunctionObjArgs(method, args, NULL);
-	} 
+	}
+	
+	/* Make sure the type is initialized. float gets initialized late */
+	if (PyType_Ready(Py_TYPE(o)) < 0)
+		return NULL;
+	
+	PyObject *method = _PyType_Lookup(Py_TYPE(o), str__sizeof__);
+	if (method == NULL)
+		PyErr_Format(PyExc_TypeError,
+			     "Type %.100s doesn't define __sizeof__",
+			     Py_TYPE(o)->tp_name);
 	else
-		return PyObject_CallMethod(args, "__sizeof__", NULL);
+		res = PyObject_CallFunctionObjArgs(method, o, NULL);
+	
+	/* Has a default value been given */
+	if ((res == NULL) && (dflt != NULL) &&
+	    PyErr_ExceptionMatches(PyExc_TypeError))
+	{
+		PyErr_Clear();
+		Py_INCREF(dflt);
+		return dflt;
+	}
+	else if (res == NULL)
+		return res;
+
+	/* add gc_head size */
+	if (PyObject_IS_GC(o)) {
+		PyObject *tmp = res;
+		res = PyNumber_Add(tmp, gc_head_size);
+		Py_DECREF(tmp);
+	}
+	return res;
 }
 
 PyDoc_STRVAR(getsizeof_doc,
-"getsizeof(object) -> int\n\
+"getsizeof(object, default) -> int\n\
 \n\
 Return the size of object in bytes.");
 
@@ -845,7 +875,8 @@
 	{"getrefcount",	(PyCFunction)sys_getrefcount, METH_O, getrefcount_doc},
 	{"getrecursionlimit", (PyCFunction)sys_getrecursionlimit, METH_NOARGS,
 	 getrecursionlimit_doc},
- 	{"getsizeof",	sys_getsizeof,  METH_O, getsizeof_doc},
+	{"getsizeof",   (PyCFunction)sys_getsizeof,
+	 METH_VARARGS | METH_KEYWORDS, getsizeof_doc},
 	{"_getframe", sys_getframe, METH_VARARGS, getframe_doc},
 #ifdef MS_WINDOWS
 	{"getwindowsversion", (PyCFunction)sys_getwindowsversion, METH_NOARGS,