diff -r 8527427914a2 Include/pystate.h
--- a/Include/pystate.h	Sat Jun 11 09:50:21 2011 -0500
+++ b/Include/pystate.h	Thu Jan 31 22:33:04 2013 +0100
@@ -180,6 +180,8 @@
 */
 PyAPI_FUNC(PyObject *) _PyThread_CurrentFrames(void);
 
+PyAPI_FUNC(void) _PyThread_AfterFork(void);
+
 /* Routines for advanced debuggers, requested by David Beazley.
    Don't use unless you know what you are doing! */
 PyAPI_FUNC(PyInterpreterState *) PyInterpreterState_Head(void);
diff -r 8527427914a2 Python/ceval.c
--- a/Python/ceval.c	Sat Jun 11 09:50:21 2011 -0500
+++ b/Python/ceval.c	Thu Jan 31 22:33:04 2013 +0100
@@ -326,6 +326,8 @@
     else
         Py_DECREF(result);
     Py_DECREF(threading);
+
+    _PyThread_AfterFork();
 }
 #endif
 
diff -r 8527427914a2 Python/pystate.c
--- a/Python/pystate.c	Sat Jun 11 09:50:21 2011 -0500
+++ b/Python/pystate.c	Thu Jan 31 22:33:04 2013 +0100
@@ -496,6 +496,14 @@
 /* Python "auto thread state" API. */
 #ifdef WITH_THREAD
 
+void
+_PyThread_AfterFork(void)
+{
+    PyThreadState *tstate = _PyThreadState_Current;
+    while (tstate->next)
+        PyThreadState_Delete(tstate->next);
+}
+
 /* Keep this as a static, as it is not reliable!  It can only
    ever be compared to the state for the *current* thread.
    * If not equal, then it doesn't matter that the actual