diff --git a/src/bcf/bcf/v2/topic.py b/src/bcf/bcf/v2/topic.py
index 975c9c84b7..d5955c5aa0 100644
--- a/src/bcf/bcf/v2/topic.py
+++ b/src/bcf/bcf/v2/topic.py
@@ -5,7 +5,7 @@ import tempfile
 import uuid
 import zipfile
 from pathlib import Path
-from typing import Any, NoReturn, Optional
+from typing import Any, NoReturn, Optional, Union
 
 import numpy as np
 from ifcopenshell import entity_instance