diff --git a/application/Espo/Entities/User.php b/application/Espo/Entities/User.php
index 7950f91db2..3fbbe91dab 100644
--- a/application/Espo/Entities/User.php
+++ b/application/Espo/Entities/User.php
@@ -43,6 +43,9 @@ class User extends Person
     public const ATTR_TYPE = 'type';
     public const ATTR_IS_ACTIVE = 'isActive';
 
+    /** @since 10.0.0 */
+    public const string FIELD_USER_NAME = 'userName';
+
     public const LINK_ACCOUNTS = 'accounts';
     public const LINK_CONTACT = 'contact';
     public const LINK_PORTALS = 'portals';
diff --git a/tests/integration/Espo/User/AccessTest.php b/tests/integration/Espo/User/AccessTest.php
new file mode 100644
index 0000000000..40df24960d
--- /dev/null
+++ b/tests/integration/Espo/User/AccessTest.php
@@ -0,0 +1,98 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM – Open Source CRM application.
+ * Copyright (C) 2014-2026 EspoCRM, Inc.
+ * 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 tests\integration\Espo\User;
+
+use Espo\Core\Exceptions\Forbidden;
+use Espo\Core\Record\ServiceContainer;
+use Espo\Entities\User;
+use tests\integration\Core\BaseTestCase;
+
+class AccessTest extends BaseTestCase
+{
+    /**
+     * @noinspection PhpUnhandledExceptionInspection
+     */
+    public function testTypeChange(): void
+    {
+        $this->createUser([
+            User::FIELD_USER_NAME => 'admin-test',
+            User::ATTR_TYPE => User::TYPE_ADMIN,
+        ]);
+
+        $this->auth('admin-test');
+        $this->reCreateApplication();
+
+        $service = $this->getContainer()
+            ->getByClass(ServiceContainer::class)
+            ->getByClass(User::class);
+
+        //
+
+        $userRegular = $service->create((object) [
+            'userName' => 'test-regular',
+            'type' => User::TYPE_REGULAR
+        ])->getEntity();
+
+        //
+
+        $thrown = false;
+
+        try {
+            $service->create((object) [
+                'userName' => 'test',
+                'type' => User::TYPE_SUPER_ADMIN,
+            ]);
+        } catch (Forbidden) {
+            $thrown = true;
+        }
+
+        $this->assertTrue($thrown);
+
+        //
+
+        $service->update($userRegular->getId(), (object) [
+            'type' => User::TYPE_ADMIN,
+        ]);
+
+        //
+
+        $thrown = false;
+
+        try {
+            $service->update($userRegular->getId(), (object) [
+                'type' => User::TYPE_SUPER_ADMIN,
+            ]);
+        } catch (Forbidden) {
+            $thrown = true;
+        }
+
+        $this->assertTrue($thrown);
+    }
+}