diff --git a/notebook/traittypes.py b/notebook/traittypes.py
index 53bb125369..dcced117b1 100644
--- a/notebook/traittypes.py
+++ b/notebook/traittypes.py
@@ -1,5 +1,6 @@
 import inspect
-from traitlets import ClassBasedTraitType, Undefined, warn
+from warnings import warn
+from traitlets import ClassBasedTraitType, Undefined
 
 # Traitlet's 5.x includes a set of utilities for building
 # description strings for objects. Traitlets 5.x does not