diff --git a/skyfield/tests/test_io.py b/skyfield/tests/test_io.py
index 29dbe2a..c0df9cc 100644
--- a/skyfield/tests/test_io.py
+++ b/skyfield/tests/test_io.py
@@ -5,7 +5,10 @@ import shutil
 import tempfile
 from contextlib import contextmanager
 from datetime import date
-from mock import patch
+try:
+    from unittest.mock import patch
+except ImportError:
+    from mock import patch
 
 from skyfield import api