diff --git a/app/models/fluentd/setting_archive/backup_file.rb b/app/models/fluentd/setting_archive/backup_file.rb
index b2d2f61..6e53063 100644
--- a/app/models/fluentd/setting_archive/backup_file.rb
+++ b/app/models/fluentd/setting_archive/backup_file.rb
@@ -13,7 +13,7 @@ class Fluentd
 
       def initialize(file_path, note = nil)
         @file_path = file_path
-        @note = note || Note.create(file_path.sub(/#{FILE_EXTENSION}$/, Note::FILE_EXTENSION))
+        @note = note || Note.create(file_path.sub(/#{Regexp.escape(FILE_EXTENSION)}$/, Note::FILE_EXTENSION))
       end
     end
   end