diff --git a/kivy/uix/widget.py b/kivy/uix/widget.py
index 76165657e..243f84c1d 100644
--- a/kivy/uix/widget.py
+++ b/kivy/uix/widget.py
@@ -336,7 +336,7 @@ class Widget(EventDispatcher):
     children = ListProperty([])
 
     #: Parent
-    parent = ObjectProperty(None)
+    parent = ObjectProperty(None, allownone=True)
 
     #: Size hint X
     size_hint_x = NumericProperty(1, allownone=True)