diff --git a/openmc/geometry.py b/openmc/geometry.py
index 01c0b2714..ee4a58a3b 100644
--- a/openmc/geometry.py
+++ b/openmc/geometry.py
@@ -2,6 +2,7 @@ from __future__ import annotations
 import os
 import typing
 from collections import OrderedDict, defaultdict
+from copy import deepcopy
 from collections.abc import Iterable
 from pathlib import Path
 import warnings