diff -r 15bfb82194fa Lib/test/test_sys.py
--- a/Lib/test/test_sys.py	Fri Aug 15 01:23:15 2014 -0400
+++ b/Lib/test/test_sys.py	Fri Aug 15 12:29:48 2014 +0300
@@ -769,6 +769,15 @@
         # but lists are
         self.assertEqual(sys.getsizeof([]), vsize('Pn') + gc_header_size)
 
+    def test_overflow(self):
+        class Overflow(int):
+            def __sizeof__(self):
+                return int(self)
+        self.assertEqual(sys.getsizeof(Overflow(sys.maxsize)),
+                         sys.maxsize + self.gc_headsize)
+        with self.assertRaises(OverflowError):
+            sys.getsizeof(Overflow(sys.maxsize + 1))
+
     def test_default(self):
         size = test.support.calcvobjsize
         self.assertEqual(sys.getsizeof(True), size('') + self.longdigit)
diff -r 15bfb82194fa Python/sysmodule.c
--- a/Python/sysmodule.c	Fri Aug 15 01:23:15 2014 -0400
+++ b/Python/sysmodule.c	Fri Aug 15 12:29:48 2014 +0300
@@ -894,6 +894,12 @@
     if (size == (size_t)-1 && PyErr_Occurred())
         return (size_t)-1;
 
+    if (size > (size_t)PY_SSIZE_T_MAX) {
+        PyErr_SetString(PyExc_OverflowError,
+                        "Python int too large to convert to C ssize_t");
+        return (size_t)-1;
+    }
+
     /* add gc_head size */
     if (PyObject_IS_GC(o))
         size += sizeof(PyGC_Head);