Index: Python/sysmodule.c
===================================================================
--- Python/sysmodule.c	(revision 64556)
+++ Python/sysmodule.c	(working copy)
@@ -643,6 +643,7 @@
 sys_getsizeof(PyObject *self, PyObject *args)
 {
 	static PyObject * str__sizeof__ = NULL;
+	PyObject *res = NULL;
 
 	/* Initialize static variable needed by _PyType_Lookup */
 	if (str__sizeof__ == NULL) {
@@ -651,26 +652,25 @@
 			return NULL;
 	}
 
-	/* Type objects */
-	if (PyType_Check(args)){
-		PyObject *method = _PyType_Lookup(Py_TYPE(args),
-						  str__sizeof__);
-		if (method == NULL) {
+	/* Make sure the type is initialized.  float gets initialized late */
+	if (PyType_Ready(Py_TYPE(args)) < 0)
+		return NULL;
+
+        /* non-type objects */
+	if (!PyType_Check(args))
+		res = PyObject_CallMethod(args, "__sizeof__", NULL);
+	/* type objects, and objects which do not have the __sizeof__ attribute */
+	if (PyType_Check(args) ||
+	    (res == NULL && PyErr_ExceptionMatches(PyExc_AttributeError))) {
+		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);
-			return NULL;
-		}
-		return PyObject_CallFunctionObjArgs(method, args, NULL);
-	} 
-	/* Instance of old-style classes */
-	else if (PyInstance_Check(args))
-		return PyInt_FromSsize_t(PyInstance_Type.tp_basicsize);
-	/* Old-style classes */
-	else if (PyClass_Check(args))
-		return PyInt_FromSsize_t(PyClass_Type.tp_basicsize);
-	else
-		return PyObject_CallMethod(args, "__sizeof__", NULL);
+		else
+			res = PyObject_CallFunctionObjArgs(method, args, NULL);
+	}
+	return res;
 }
 
 PyDoc_STRVAR(getsizeof_doc,
Index: Lib/test/test_sys.py
===================================================================
--- Lib/test/test_sys.py	(revision 64556)
+++ Lib/test/test_sys.py	(working copy)
@@ -559,7 +559,25 @@
         self.check_sizeof((), size(h))
         self.check_sizeof((1,2,3), size(h) + 3*self.P)
 
+    def test_moduleobjects(self):
+        # Some objects from built-in modules
+        h = self.header
+        size = self.calcsize
 
+        # _sre.PatternObject
+        import re
+        x = re.compile("")
+        self.check_sizeof(x, size(h + 'P PPP PiP PH'))
+
+        # _sre.Match
+        x = re.match('','')
+        self.check_sizeof(x, 42)
+        
+        # _struct.Struct
+        x = struct.Struct("")
+        self.check_sizeof(x, size(h + 'PPPPP'))
+
+
 def test_main():
     test_classes = (SysModuleTest, SizeofTest)
 
Index: Modules/_sre.c
===================================================================
--- Modules/_sre.c	(revision 64556)
+++ Modules/_sre.c	(working copy)
@@ -3083,6 +3083,11 @@
 #endif
 }
 
+static PyObject*
+match_sizeof(MatchObject *self) {
+	return PyInt_FromSsize_t(42);
+}
+
 static PyMethodDef match_methods[] = {
     {"group", (PyCFunction) match_group, METH_VARARGS},
     {"start", (PyCFunction) match_start, METH_VARARGS},
@@ -3093,6 +3098,7 @@
     {"expand", (PyCFunction) match_expand, METH_O},
     {"__copy__", (PyCFunction) match_copy, METH_NOARGS},
     {"__deepcopy__", (PyCFunction) match_deepcopy, METH_O},
+    {"__sizeof__", (PyCFunction) match_sizeof, METH_NOARGS},
     {NULL, NULL}
 };