diff --git a/bugsnag/utils.py b/bugsnag/utils.py
index 0286af2..8a55798 100644
--- a/bugsnag/utils.py
+++ b/bugsnag/utils.py
@@ -6,7 +6,8 @@
 import warnings
 import copy
 import logging
-from datetime import datetime, timedelta, timezone
+from datetime import datetime, timedelta
+import sys
 from urllib.parse import urlparse, urlunsplit, parse_qs