diff --git a/Classes/ErrorHandler.php b/Classes/ErrorHandler.php
index fd90a64..314ed5d 100644
--- a/Classes/ErrorHandler.php
+++ b/Classes/ErrorHandler.php
@@ -138,7 +138,7 @@ protected function getPageUid_403($fe_group)
     protected function getExtConf()
     {
         if (is_null($this->extConf)) {
-            $this->extConf = $GLOBALS['TYPO3_CONF_VARS']['EXTENSIONS']['fox_handler'];
+            $this->extConf = $GLOBALS['TYPO3_CONF_VARS']['EXTENSIONS']['fox_handler'] ?? [];
         }
 
         return $this->extConf;
diff --git a/composer.json b/composer.json
index eee2bdf..49449ed 100644
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,7 @@
     "TYPO3 CMS"
   ],
   "require": {
-    "typo3/cms-core": "^10.4 || ^11.5"
+    "typo3/cms-core": "^10.4 || ^11.5 || ^12.4 || ^13.4"
   },
   "autoload": {
     "psr-4": {
diff --git a/ext_emconf.php b/ext_emconf.php
index d740828..b293d02 100644
--- a/ext_emconf.php
+++ b/ext_emconf.php
@@ -14,7 +14,7 @@
     'version' => '4.0.1',
     'constraints' => [
         'depends' => [
-            'typo3' => '10.4.0-11.5.99',
+            'typo3' => '10.4.0-13.4.99',
         ],
         'conflicts' => [],
         'suggests' => [],