Index: Objects/typeobject.c
===================================================================
--- Objects/typeobject.c	(revision 69434)
+++ Objects/typeobject.c	(working copy)
@@ -4618,7 +4618,12 @@
 
 	if (res == NULL)
 		return -1;
-	len = PyLong_AsSsize_t(res);
+	if (!PyNumber_Check(res)) {
+		PyErr_SetString(PyExc_TypeError,
+				"__len__ returned non number value");
+		return -1;
+	}
+	len = PyNumber_AsSsize_t(res, PyExc_OverflowError);
 	Py_DECREF(res);
 	if (len < 0) {
 		if (!PyErr_Occurred())
Index: Lib/test/test_builtin.py
===================================================================
--- Lib/test/test_builtin.py	(revision 69434)
+++ Lib/test/test_builtin.py	(working copy)
@@ -611,6 +611,18 @@
             def __len__(self):
                 raise ValueError
         self.assertRaises(ValueError, len, BadSeq())
+        class InvalidLen:
+            def __len__(self):
+                return None
+        self.assertRaises(TypeError, len, InvalidLen())
+        class FloatLen:
+            def __len__(self):
+                return 4.5
+        self.assertRaises(TypeError, len, FloatLen())
+        class HugeLen:
+            def __len__(self):
+                return sys.maxsize + 1
+        self.assertRaises(OverflowError, len, HugeLen())
 
     def test_map(self):
         self.assertEqual(