From 3ebc5288406fe11951dbc2df39bcf884b150fc70 Mon Sep 17 00:00:00 2001
From: Min RK <benjaminrk@gmail.com>
Date: Tue, 8 Aug 2017 14:40:36 +0200
Subject: [PATCH] disable cross-validation of defaults

---
 traitlets/traitlets.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/traitlets/traitlets.py b/traitlets/traitlets.py
index df06228b..a36d9334 100644
--- a/traitlets/traitlets.py
+++ b/traitlets/traitlets.py
@@ -519,7 +519,8 @@ def get(self, obj, cls=None):
                 raise TraitError("No default value found for "
                     "the '%s' trait named '%s' of %r" % (
                     type(self).__name__, self.name, obj))
-            value = self._validate(obj, default)
+            with obj.cross_validation_lock:
+                value = self._validate(obj, default)
             obj._trait_values[self.name] = value
             obj.notify_change(Bunch(
                 name=self.name,