diff --git a/src/flask_session/sessions.py b/src/flask_session/sessions.py
index a4346f2b..98322241 100644
--- a/src/flask_session/sessions.py
+++ b/src/flask_session/sessions.py
@@ -433,7 +433,9 @@ def fetch_session_sid(self, sid):
         store_id = self.key_prefix + sid
         saved_session = self.sql_session_model.query.filter_by(
             session_id=store_id).first()
-        if saved_session and saved_session.expiry <= datetime.utcnow():
+        if saved_session and (
+            not saved_session.expiry or saved_session.expiry <= datetime.utcnow()
+        ):
             # Delete expired session
             self.db.session.delete(saved_session)
             self.db.session.commit()