diff --git a/cain/types/__init__.py b/cain/types/__init__.py
index a843fd1..0436006 100644
--- a/cain/types/__init__.py
+++ b/cain/types/__init__.py
@@ -54,7 +54,7 @@ def retrieve_type(datatype: typing.Union[typing.Type[model.Datatype],
 
     datatype = typing.get_origin(datatype) or datatype
 
-    if datatype == typing.Union:
+    if datatype is typing.Union:
         return Union, type_args
 
     if datatype is None or datatype is NONE_TYPE: