diff --git a/lib/fluent/supervisor.rb b/lib/fluent/supervisor.rb
index 59d52380e3..d5bf26634b 100644
--- a/lib/fluent/supervisor.rb
+++ b/lib/fluent/supervisor.rb
@@ -449,7 +449,6 @@ def initialize(opt)
       @plugin_dirs = opt[:plugin_dirs]
       @chgroup = opt[:chgroup]
       @chuser = opt[:chuser]
-      @rpc_server = nil
       @process_name = nil
 
       @workers = opt[:workers]