diff -r f1a25c088b8f Lib/test/test_range.py
--- a/Lib/test/test_range.py	Fri Nov 02 14:49:02 2012 +0100
+++ b/Lib/test/test_range.py	Sun Nov 04 11:28:38 2012 +0000
@@ -312,6 +312,15 @@
 
         self.assertRaises(TypeError, range, IN())
 
+        # Test use of user-defined classes in slice indices.
+        self.assertEqual(range(10)[:I(5)], range(5))
+
+        with self.assertRaises(RuntimeError):
+            range(0, 10)[:IX()]
+
+        with self.assertRaises(TypeError):
+            range(0, 10)[:IN()]
+
     def test_count(self):
         self.assertEqual(range(3).count(-1), 0)
         self.assertEqual(range(3).count(0), 1)
diff -r f1a25c088b8f Objects/rangeobject.c
--- a/Objects/rangeobject.c	Fri Nov 02 14:49:02 2012 +0100
+++ b/Objects/rangeobject.c	Sun Nov 04 11:28:38 2012 +0000
@@ -331,11 +331,11 @@
         if (PyIndex_Check(obj)) {
             result = PyNumber_Index(obj);
         }
-    }
-    if (result == NULL) {
-        PyErr_SetString(PyExc_TypeError,
-                        "slice indices must be integers or "
-                        "None or have an __index__ method");
+        else {
+            PyErr_SetString(PyExc_TypeError,
+                            "slice indices must be integers or "
+                            "None or have an __index__ method");
+        }
     }
     return result;
 }