diff --git a/plugins/bc-mail/config/Seeds/MailFieldsSeed.php b/plugins/bc-mail/config/Seeds/MailFieldsSeed.php
index 2d206a0e71..c116259013 100644
--- a/plugins/bc-mail/config/Seeds/MailFieldsSeed.php
+++ b/plugins/bc-mail/config/Seeds/MailFieldsSeed.php
@@ -97,7 +97,7 @@ public function run(): void
                 'source' => '男性|女性',
                 'size' => 0,
                 'text_rows' => 0,
-                'maxlength' => 0,
+                'maxlength' => NULL,
                 'options' => '',
                 'class' => '',
                 'default_value' => '',
@@ -346,7 +346,7 @@ public function run(): void
                 'source' => '資料請求|問い合わせ|その他',
                 'size' => 0,
                 'text_rows' => 0,
-                'maxlength' => 0,
+                'maxlength' => NULL,
                 'options' => '',
                 'class' => '',
                 'default_value' => '',
@@ -408,7 +408,7 @@ public function run(): void
                 'source' => '検索エンジン|web広告|紙面広告|求人案内|その他',
                 'size' => 0,
                 'text_rows' => 0,
-                'maxlength' => 0,
+                'maxlength' => NULL,
                 'options' => '',
                 'class' => '',
                 'default_value' => '',