From 15a37c9ba7c969bb246dc90459ba2244baa5dd8e Mon Sep 17 00:00:00 2001
From: Ryan Morshead <ryan.morshead@gmail.com>
Date: Wed, 2 Nov 2016 11:48:06 -0700
Subject: [PATCH] fix for default value changes in ipython/traitlets/pull/332

---
 notebook/services/contents/manager.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/notebook/services/contents/manager.py b/notebook/services/contents/manager.py
index 3974bb252..8918b474a 100644
--- a/notebook/services/contents/manager.py
+++ b/notebook/services/contents/manager.py
@@ -74,7 +74,7 @@ class ContentsManager(LoggingConfigurable):
         help="The base name used when creating untitled directories."
     )
 
-    pre_save_hook = Any(None, config=True,
+    pre_save_hook = Any(None, config=True, allow_none=True,
         help="""Python callable or importstring thereof
 
         To be called on a contents model prior to save.