diff --git a/src/modeci_mdf/functions/standard.py b/src/modeci_mdf/functions/standard.py
index e5215c8b..b3d1b015 100644
--- a/src/modeci_mdf/functions/standard.py
+++ b/src/modeci_mdf/functions/standard.py
@@ -5,7 +5,7 @@
 
 """
 import warnings
-
+import types
 from typing import List, Dict, Callable
 
 from docstring_parser import parse