diff --git a/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php b/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php
index 86378fb4bda2e606804e65453f57c27f9c2f5c5a..c6d716a022e68010347500271e52e3f7fb76e2d1 100644
--- a/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php
+++ b/typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php
@@ -463,6 +463,7 @@ class BackendUserAuthentication extends AbstractUserAuthentication
             return true;
         }
         $systemMaintainers = $GLOBALS['TYPO3_CONF_VARS']['SYS']['systemMaintainers'] ?? [];
+        $systemMaintainers = array_map('intval', $systemMaintainers);
         if (!empty($systemMaintainers)) {
             return in_array($this->getRealUserId(), $systemMaintainers, true);
         }
diff --git a/typo3/sysext/install/Classes/Controller/SettingsController.php b/typo3/sysext/install/Classes/Controller/SettingsController.php
index 592c88a6cae77db2f833410213c0d38eb61ee248..35d4292e993ea78656aade525203ecbdc3a9dcd3 100644
--- a/typo3/sysext/install/Classes/Controller/SettingsController.php
+++ b/typo3/sysext/install/Classes/Controller/SettingsController.php
@@ -124,6 +124,7 @@ class SettingsController extends AbstractController
             ->fetchAll();
 
         $systemMaintainerList = $GLOBALS['TYPO3_CONF_VARS']['SYS']['systemMaintainers'] ?? [];
+        $systemMaintainerList = array_map('intval', $systemMaintainerList);
         $currentTime = time();
         foreach ($users as &$user) {
             $user['disable'] = $user['disable'] ||
@@ -172,6 +173,7 @@ class SettingsController extends AbstractController
             )->execute()->fetchAll();
 
         $validatedUserList = array_column($validatedUserList, 'uid');
+        $validatedUserList = array_map('intval', $validatedUserList);
 
         $configurationManager = GeneralUtility::makeInstance(ConfigurationManager::class);
         $configurationManager->setLocalConfigurationValuesByPathValuePairs(