diff -r ff983ee10b3e Lib/test/test_generators.py
--- a/Lib/test/test_generators.py	Thu May 21 12:03:21 2015 -0400
+++ b/Lib/test/test_generators.py	Thu May 21 12:23:28 2015 -0400
@@ -1,6 +1,7 @@
 import gc
 import sys
 import unittest
+import warnings
 import weakref
 
 from test import support
@@ -217,6 +218,24 @@
         self.assertEqual(next(g), "done")
         self.assertEqual(sys.exc_info(), (None, None, None))
 
+    def test_stopiteration_warning(self):
+        # See also PEP 479.
+
+        def gen():
+            raise StopIteration
+            yield
+
+        with self.assertRaises(StopIteration), warnings.catch_warnings():
+            warnings.simplefilter('ignore')
+            next(gen())
+
+        with self.assertRaisesRegex(PendingDeprecationWarning,
+                                    "generator .* raised StopIteration"), \
+             warnings.catch_warnings():
+
+            warnings.simplefilter('error')
+            next(gen())
+
 
 tutorial_tests = """
 Let's try a simple generator:
diff -r ff983ee10b3e Objects/genobject.c
--- a/Objects/genobject.c	Thu May 21 12:03:21 2015 -0400
+++ b/Objects/genobject.c	Thu May 21 12:23:28 2015 -0400
@@ -143,13 +143,12 @@
         }
         Py_CLEAR(result);
     }
-    else if (!result) {
+    else if (!result && PyErr_ExceptionMatches(PyExc_StopIteration)) {
         /* Check for __future__ generator_stop and conditionally turn
          * a leaking StopIteration into RuntimeError (with its cause
          * set appropriately). */
-        if ((((PyCodeObject *)gen->gi_code)->co_flags &
+        if (((PyCodeObject *)gen->gi_code)->co_flags &
               (CO_FUTURE_GENERATOR_STOP | CO_COROUTINE | CO_ITERABLE_COROUTINE))
-            && PyErr_ExceptionMatches(PyExc_StopIteration))
         {
             PyObject *exc, *val, *val2, *tb;
             PyErr_Fetch(&exc, &val, &tb);
@@ -167,6 +166,24 @@
             PyException_SetContext(val2, val);
             PyErr_Restore(exc, val2, tb);
         }
+        else {
+            PyObject *exc, *val, *tb;
+
+            /* Pop the exception before issuing a warning. */
+            PyErr_Fetch(&exc, &val, &tb);
+
+            if (PyErr_WarnFormat(PyExc_PendingDeprecationWarning, 1,
+                                 "generator '%.50S' raised StopIteration",
+                                 gen->gi_qualname)) {
+                /* Warning was converted to an error. */
+                Py_XDECREF(exc);
+                Py_XDECREF(val);
+                Py_XDECREF(tb);
+            }
+            else {
+                PyErr_Restore(exc, val, tb);
+            }
+        }
     }
 
     if (!result || f->f_stacktop == NULL) {