diff --git a/lib/fluent/command/fluentd.rb b/lib/fluent/command/fluentd.rb
index d77be34bd4..5dd9851f3c 100644
--- a/lib/fluent/command/fluentd.rb
+++ b/lib/fluent/command/fluentd.rb
@@ -344,6 +344,7 @@
 end
 
 if fluentdopt = opts[:fluentdopt]
+  require "win32/registry"
   Win32::Registry::HKEY_LOCAL_MACHINE.open("SYSTEM\\CurrentControlSet\\Services\\#{opts[:winsvc_name]}", Win32::Registry::KEY_ALL_ACCESS) do |reg|
     reg['fluentdopt', Win32::Registry::REG_SZ] = fluentdopt
   end