diff --git a/lib/fluent/supervisor.rb b/lib/fluent/supervisor.rb
index a76bd1d40a..07835b96ee 100644
--- a/lib/fluent/supervisor.rb
+++ b/lib/fluent/supervisor.rb
@@ -450,7 +450,7 @@ def self.serverengine_config(params = {})
         stop_immediately_at_unrecoverable_exit: true,
         root_dir: params['root_dir'],
         logger: $log,
-        log: $log.out,
+        log: $log&.out,
         log_level: params['log_level'],
         chuser: params['chuser'],
         chgroup: params['chgroup'],