diff --git a/voluptuous_serialize/__init__.py b/voluptuous_serialize/__init__.py
index 135ffbf..2180c2f 100644
--- a/voluptuous_serialize/__init__.py
+++ b/voluptuous_serialize/__init__.py
@@ -118,7 +118,7 @@ def convert(schema, *, custom_serializer=None):
     if isinstance(schema, (str, int, float, bool)):
         return {"type": "constant", "value": schema}
 
-    if issubclass(schema, Enum):
+    if if isinstance(schema, type) and issubclass(schema, Enum):
         return {
             "type": "select",
             "options": [(item.value, item.value) for item in schema],