diff --git a/nova/scheduler/least_cost.py b/nova/scheduler/least_cost.py
index 6f5eb66fd..8c400d476 100644
--- a/nova/scheduler/least_cost.py
+++ b/nova/scheduler/least_cost.py
@@ -28,6 +28,7 @@ from nova import flags
 from nova import log as logging
 from nova.scheduler import zone_aware_scheduler
 from nova import utils
+from nova import exception
 
 LOG = logging.getLogger('nova.scheduler.least_cost')