diff --git a/app/controllers/concerns/setting_history_concern.rb b/app/controllers/concerns/setting_history_concern.rb
index 12accf3..72c43af 100644
--- a/app/controllers/concerns/setting_history_concern.rb
+++ b/app/controllers/concerns/setting_history_concern.rb
@@ -28,7 +28,7 @@ module SettingHistoryConcern
     else
       flash = { danger: @fluentd.agent.log.tail(1).first }
     end
-    redirect_to :back, flash: flash
+    redirect_back fallback_location: root_url, flash: flash
   end
 
 end