diff --git a/application/Espo/Classes/FieldValidators/Settings/ThousandSeparator/Valid.php b/application/Espo/Classes/FieldValidators/Settings/ThousandSeparator/Valid.php
new file mode 100644
index 0000000000..ade7bb9ce6
--- /dev/null
+++ b/application/Espo/Classes/FieldValidators/Settings/ThousandSeparator/Valid.php
@@ -0,0 +1,60 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM – Open Source CRM application.
+ * Copyright (C) 2014-2024 Yurii Kuznietsov, Taras Machyshyn, Oleksii Avramenko
+ * Website: https://www.espocrm.com
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * The interactive user interfaces in modified source and object code versions
+ * of this program must display Appropriate Legal Notices, as required under
+ * Section 5 of the GNU Affero General Public License version 3.
+ *
+ * In accordance with Section 7(b) of the GNU Affero General Public License version 3,
+ * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
+ ************************************************************************/
+
+namespace Espo\Classes\FieldValidators\Settings\ThousandSeparator;
+
+use Espo\Core\FieldValidation\Validator;
+use Espo\Core\FieldValidation\Validator\Data;
+use Espo\Core\FieldValidation\Validator\Failure;
+use Espo\ORM\Entity;
+
+/**
+ * @implements Validator<Entity>
+ */
+class Valid implements Validator
+{
+    public function validate(Entity $entity, string $field, Data $data): ?Failure
+    {
+        $value = $entity->get($field);
+
+        if (!$value) {
+            return null;
+        }
+
+        if (!is_string($value)) {
+            return Failure::create();
+        }
+
+        if (preg_match('/^[0-9]$/', $value)) {
+            return Failure::create();
+        }
+
+        return null;
+    }
+}
diff --git a/application/Espo/Resources/metadata/entityDefs/Preferences.json b/application/Espo/Resources/metadata/entityDefs/Preferences.json
index 543a0f8e13..577c47504c 100644
--- a/application/Espo/Resources/metadata/entityDefs/Preferences.json
+++ b/application/Espo/Resources/metadata/entityDefs/Preferences.json
@@ -31,6 +31,9 @@
                 ".",
                 ",",
                 "'"
+            ],
+            "validatorClassNameList": [
+                "Espo\\Classes\\FieldValidators\\Settings\\ThousandSeparator\\Valid"
             ]
         },
         "decimalMark": {
diff --git a/application/Espo/Resources/metadata/entityDefs/Settings.json b/application/Espo/Resources/metadata/entityDefs/Settings.json
index f0437d8b95..6723edf33a 100644
--- a/application/Espo/Resources/metadata/entityDefs/Settings.json
+++ b/application/Espo/Resources/metadata/entityDefs/Settings.json
@@ -155,6 +155,9 @@
                 ".",
                 ",",
                 "'"
+            ],
+            "validatorClassNameList": [
+                "Espo\\Classes\\FieldValidators\\Settings\\ThousandSeparator\\Valid"
             ]
         },
         "decimalMark": {