diff --git a/nipype/interfaces/io.py b/nipype/interfaces/io.py
index 472c40c248..ccf20ebcb1 100644
--- a/nipype/interfaces/io.py
+++ b/nipype/interfaces/io.py
@@ -2943,7 +2943,7 @@ def __init__(self, infields=None, **kwargs):
         undefined_traits = {}
         for key in self._infields:
             self.inputs.add_trait(key, traits.Any)
-            undefined_traits[key] = kwargs[key] if key in kwargs else Undefined
+            undefined_traits[key] = kwargs.get(key, Undefined)
 
         self.inputs.trait_set(trait_change_notify=False, **undefined_traits)