Index: Lib/threading.py
===================================================================
--- Lib/threading.py	(revision 66872)
+++ Lib/threading.py	(working copy)
@@ -733,10 +733,10 @@
 
     def __init__(self):
         Thread.__init__(self, name="MainThread")
-        self._Thread__started.set()
         _active_limbo_lock.acquire()
         _active[_get_ident()] = self
         _active_limbo_lock.release()
+        self._Thread__started.set()
 
     def _set_daemon(self):
         return False
@@ -779,10 +779,10 @@
         # instance is immortal, that's bad, so release this resource.
         del self._Thread__block
 
-        self._Thread__started.set()
         _active_limbo_lock.acquire()
         _active[_get_ident()] = self
         _active_limbo_lock.release()
+        self._Thread__started.set()
 
     def _set_daemon(self):
         return True