diff --git a/app/models/fluentd/setting/in_tail.rb b/app/models/fluentd/setting/in_tail.rb
index 044815b..1d160bb 100644
--- a/app/models/fluentd/setting/in_tail.rb
+++ b/app/models/fluentd/setting/in_tail.rb
@@ -1,6 +1,8 @@
 class Fluentd
   module Setting
     class InTail
+      MULTI_LINE_MAX_FORMAT_COUNT = 20
+
       include ActiveModel::Model
       attr_accessor :path, :tag, :format, :regexp, :time_format, :rotate_wait, :pos_file, :read_from_head, :refresh_interval
 
@@ -18,7 +20,7 @@ class Fluentd
           :ltsv => [:delimiter, :time_key],
           :json => [:time_key],
           :regexp => [:time_format, :regexp],
-          :multiline => [:format_firstline] + (1..20).map{|n| "format#{n}".to_sym }
+          :multiline => [:format_firstline] + (1..MULTI_LINE_MAX_FORMAT_COUNT).map{|n| "format#{n}".to_sym }
           # TODO: Grok could generate Regexp including \d, \s, etc. fluentd config parser raise error with them for escape sequence check.
           #       TBD How to handle Grok/Regexp later, just comment out for hide
           # :grok => [:grok_str],