diff --git a/devstack/files/monasca-log-metrics/log-metrics.conf b/devstack/files/monasca-log-metrics/log-metrics.conf
index cf7447345..e48468be6 100644
--- a/devstack/files/monasca-log-metrics/log-metrics.conf
+++ b/devstack/files/monasca-log-metrics/log-metrics.conf
@@ -29,7 +29,7 @@ input {
 filter {
 
   # drop logs that have not set log level
-  if "level" not in [log] {
+  if ![log][level] {
     drop { periodic_flush => true }
   } else {
     ruby {