diff --git a/Lib/multiprocessing/dummy/__init__.py b/Lib/multiprocessing/dummy/__init__.py
index c4933d9ec53..101c3cba4d7 100644
--- a/Lib/multiprocessing/dummy/__init__.py
+++ b/Lib/multiprocessing/dummy/__init__.py
@@ -70,7 +70,8 @@ def __init__(self, group=None, target=None, name=None, args=(), kwargs={}):
     def start(self):
         assert self._parent is current_process()
         self._start_called = True
-        self._parent._children[self] = None
+        if hasattr(self._parent, '_children'):
+            self._parent._children[self] = None
         threading.Thread.start(self)
 
     @property