diff -r 89521ac669f0 Include/ceval.h
--- a/Include/ceval.h	Sun May 31 21:44:15 2015 -0400
+++ b/Include/ceval.h	Sun May 31 22:03:14 2015 -0400
@@ -23,8 +23,9 @@
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(void) PyEval_SetProfile(Py_tracefunc, PyObject *);
 PyAPI_FUNC(void) PyEval_SetTrace(Py_tracefunc, PyObject *);
-PyAPI_FUNC(void) PyEval_SetCoroutineWrapper(PyObject *wrapper);
-PyAPI_FUNC(PyObject *) PyEval_GetCoroutineWrapper(void);
+PyAPI_FUNC(void) _PyEval_SetCoroutineWrapper(PyObject *wrapper);
+PyAPI_FUNC(PyObject *) _PyEval_GetCoroutineWrapper(void);
+PyAPI_FUNC(PyObject *) _PyEval_ApplyCoroutineWrapper(PyObject *gen);
 #endif
 
 struct _frame; /* Avoid including frameobject.h */
diff -r 89521ac669f0 Include/pystate.h
--- a/Include/pystate.h	Sun May 31 21:44:15 2015 -0400
+++ b/Include/pystate.h	Sun May 31 22:03:14 2015 -0400
@@ -135,6 +135,7 @@
     void *on_delete_data;
 
     PyObject *coroutine_wrapper;
+    int in_coroutine_wrapper;
 
     /* XXX signal handlers should also be here */
 
diff -r 89521ac669f0 Python/ceval.c
--- a/Python/ceval.c	Sun May 31 21:44:15 2015 -0400
+++ b/Python/ceval.c	Sun May 31 22:03:14 2015 -0400
@@ -3921,7 +3921,6 @@
 
     if (co->co_flags & CO_GENERATOR) {
         PyObject *gen;
-        PyObject *coroutine_wrapper;
 
         /* Don't need to keep the reference to f_back, it will be set
          * when the generator is resumed. */
@@ -3935,14 +3934,9 @@
         if (gen == NULL)
             return NULL;
 
-        if (co->co_flags & (CO_COROUTINE | CO_ITERABLE_COROUTINE)) {
-            coroutine_wrapper = PyEval_GetCoroutineWrapper();
-            if (coroutine_wrapper != NULL) {
-                PyObject *wrapped =
-                            PyObject_CallFunction(coroutine_wrapper, "N", gen);
-                gen = wrapped;
-            }
-        }
+        if (co->co_flags & (CO_COROUTINE | CO_ITERABLE_COROUTINE))
+            return _PyEval_ApplyCoroutineWrapper(gen);
+
         return gen;
     }
 
@@ -4390,7 +4384,7 @@
 }
 
 void
-PyEval_SetCoroutineWrapper(PyObject *wrapper)
+_PyEval_SetCoroutineWrapper(PyObject *wrapper)
 {
     PyThreadState *tstate = PyThreadState_GET();
 
@@ -4401,13 +4395,36 @@
 }
 
 PyObject *
-PyEval_GetCoroutineWrapper(void)
+_PyEval_GetCoroutineWrapper(void)
 {
     PyThreadState *tstate = PyThreadState_GET();
     return tstate->coroutine_wrapper;
 }
 
 PyObject *
+_PyEval_ApplyCoroutineWrapper(PyObject *gen)
+{
+    PyObject *wrapped;
+    PyThreadState *tstate = PyThreadState_GET();
+    PyObject *wrapper = tstate->coroutine_wrapper;
+
+    if (tstate->in_coroutine_wrapper) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "Cannot call coroutine wrapper recursively");
+        return NULL;
+    }
+
+    if (wrapper == NULL) {
+        return gen;
+    }
+
+    tstate->in_coroutine_wrapper = 1;
+    wrapped = PyObject_CallFunction(wrapper, "N", gen);
+    tstate->in_coroutine_wrapper = 0;
+    return wrapped;
+}
+
+PyObject *
 PyEval_GetBuiltins(void)
 {
     PyFrameObject *current_frame = PyEval_GetFrame();
diff -r 89521ac669f0 Python/pystate.c
--- a/Python/pystate.c	Sun May 31 21:44:15 2015 -0400
+++ b/Python/pystate.c	Sun May 31 22:03:14 2015 -0400
@@ -213,6 +213,7 @@
         tstate->on_delete_data = NULL;
 
         tstate->coroutine_wrapper = NULL;
+        tstate->in_coroutine_wrapper = 0;
 
         if (init)
             _PyThreadState_Init(tstate);
diff -r 89521ac669f0 Python/sysmodule.c
--- a/Python/sysmodule.c	Sun May 31 21:44:15 2015 -0400
+++ b/Python/sysmodule.c	Sun May 31 22:03:14 2015 -0400
@@ -655,10 +655,10 @@
                          Py_TYPE(wrapper)->tp_name);
             return NULL;
         }
-        PyEval_SetCoroutineWrapper(wrapper);
+        _PyEval_SetCoroutineWrapper(wrapper);
     }
     else {
-        PyEval_SetCoroutineWrapper(NULL);
+        _PyEval_SetCoroutineWrapper(NULL);
     }
     Py_RETURN_NONE;
 }
@@ -672,7 +672,7 @@
 static PyObject *
 sys_get_coroutine_wrapper(PyObject *self, PyObject *args)
 {
-    PyObject *wrapper = PyEval_GetCoroutineWrapper();
+    PyObject *wrapper = _PyEval_GetCoroutineWrapper();
     if (wrapper == NULL) {
         wrapper = Py_None;
     }