diff -r 64fba4ea031b Objects/genobject.c
--- a/Objects/genobject.c	Wed May 20 23:07:02 2015 -0400
+++ b/Objects/genobject.c	Wed May 20 23:57:34 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 +166,25 @@
             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)) {
+                if (PyErr_ExceptionMatches(PyExc_Warning)) {
+                    PyErr_WriteUnraisable((PyObject *) gen);
+                }
+                else {
+                    return NULL;
+                }
+            }
+
+            PyErr_Restore(exc, val, tb);
+        }
     }
 
     if (!result || f->f_stacktop == NULL) {