diff --git a/fire/inspectutils.py b/fire/inspectutils.py
index 0fa8e7d3..268150ec 100644
--- a/fire/inspectutils.py
+++ b/fire/inspectutils.py
@@ -23,6 +23,7 @@
 import types
 
 from fire import docstrings
+from typing import get_args
 
 import six
 
@@ -143,7 +144,7 @@ def Py3GetFullArgSpec(fn):
 
   if sig.return_annotation is not sig.empty:
     annotations['return'] = sig.return_annotation
-
+  
   for param in sig.parameters.values():
     kind = param.kind
     name = param.name
@@ -165,6 +166,10 @@ def Py3GetFullArgSpec(fn):
       varkw = name
     if param.annotation is not param.empty:
       annotations[name] = param.annotation
+      if "Union" in str(annotations[name]):
+        union_type_tuple = get_args(annotations[name])
+        annotations[name] = union_type_tuple[0]
+
     # pylint: enable=protected-access
 
   if not kwdefaults: