diff --git a/django_celery_results/backends/database.py b/django_celery_results/backends/database.py
index 7353bc6f..b2778f4a 100644
--- a/django_celery_results/backends/database.py
+++ b/django_celery_results/backends/database.py
@@ -194,6 +194,8 @@ def _forget(self, task_id):
 
     def cleanup(self):
         """Delete expired metadata."""
+        if not self.expires:
+            return
         self.TaskModel._default_manager.delete_expired(self.expires)
         self.GroupModel._default_manager.delete_expired(self.expires)