diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index fdb2df47ed8d..e704c90ebd12 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -167,8 +167,10 @@ interval_opts = [
                help="Number of seconds between instance network information "
                     "cache updates"),
     cfg.IntOpt('reclaim_instance_interval',
+               min=0,
                default=0,
-               help='Interval in seconds for reclaiming deleted instances'),
+               help='Interval in seconds for reclaiming deleted instances. '
+                    'It takes effect only when value is greater than 0.'),
     cfg.IntOpt('volume_usage_poll_interval',
                default=0,
                help='Interval in seconds for gathering volume usages'),