diff --git a/app/Repositories/SettingRepository.php b/app/Repositories/SettingRepository.php
index c483fbc1..fe92bc93 100644
--- a/app/Repositories/SettingRepository.php
+++ b/app/Repositories/SettingRepository.php
@@ -52,6 +52,7 @@ class SettingRepository extends BaseRepository
         do_log("sql: $sql, result: $result");
         NexusDB::cache_del("nexus_settings_in_laravel");
         NexusDB::cache_del("nexus_settings_in_nexus");
+        NexusDB::cache_del('setting_protected_forum');
         return $result;
     }
 
diff --git a/include/globalfunctions.php b/include/globalfunctions.php
index 8d9d4d93..2206ffa4 100644
--- a/include/globalfunctions.php
+++ b/include/globalfunctions.php
@@ -1025,6 +1025,7 @@ function clear_setting_cache()
     do_log("clear_setting_cache");
     \Nexus\Database\NexusDB::cache_del('nexus_settings_in_laravel');
     \Nexus\Database\NexusDB::cache_del('nexus_settings_in_nexus');
+    \Nexus\Database\NexusDB::cache_del('setting_protected_forum');
     $channel = nexus_env("CHANNEL_NAME_SETTING");
     if (!empty($channel)) {
         \Nexus\Database\NexusDB::redis()->publish($channel, "update");
diff --git a/lang/chs/lang_takeinvite.php b/lang/chs/lang_takeinvite.php
index 605dddc9..c317024b 100644
--- a/lang/chs/lang_takeinvite.php
+++ b/lang/chs/lang_takeinvite.php
@@ -3,6 +3,7 @@
 $lang_takeinvite = array
 (
 	'head_invitation_failed' => "邀请失败！",
+	'std_username_too_long' => "对不起，用户名过长（至多12个字符）",
 	'std_must_enter_email' => "你必须输入邮箱地址！",
 	'std_invalid_email_address' => "无效的邮箱地址！",
 	'std_must_enter_personal_message' => "请添加信件中的私人内容。",
diff --git a/lang/cht/lang_takeinvite.php b/lang/cht/lang_takeinvite.php
index e4c2e8f3..b5e13c59 100644
--- a/lang/cht/lang_takeinvite.php
+++ b/lang/cht/lang_takeinvite.php
@@ -3,6 +3,7 @@
 $lang_takeinvite = array
 (
 	'head_invitation_failed' => "邀請失敗！",
+	'std_username_too_long' => "對不起，用戶名過長（至多12個字元）",
 	'std_must_enter_email' => "你必須輸入郵箱位址！",
 	'std_invalid_email_address' => "無效的郵箱地址！",
 	'std_must_enter_personal_message' => "請添加信件中的私人內容。",
diff --git a/lang/en/lang_takeinvite.php b/lang/en/lang_takeinvite.php
index ddbbf75c..03b6a0cc 100644
--- a/lang/en/lang_takeinvite.php
+++ b/lang/en/lang_takeinvite.php
@@ -3,6 +3,7 @@
 $lang_takeinvite = array
 (
 	'head_invitation_failed' => "Invitation failed!",
+	'std_username_too_long' => "Sorry, the username is too long (up to 12 characters)",
 	'std_must_enter_email' => "You must enter an email address!",
 	'std_invalid_email_address' => "Invalid email address!",
 	'std_must_enter_personal_message' => "Please add a personal message.",
diff --git a/public/takeinvite.php b/public/takeinvite.php
index f65a1e41..8642839a 100644
--- a/public/takeinvite.php
+++ b/public/takeinvite.php
@@ -21,6 +21,8 @@ $email = unesc(htmlspecialchars(trim($_POST["email"])));
 $email = safe_email($email);
 $preRegisterUsername = $_POST['pre_register_username'] ?? '';
 $isPreRegisterEmailAndUsername = get_setting("system.is_invite_pre_email_and_username") == "yes";
+if (strlen($preRegisterUsername) > 12)
+	bark($lang_takeinvite['std_username_too_long']);
 if (!$email)
     bark($lang_takeinvite['std_must_enter_email']);
 if (!check_email($email))