diff --git a/typo3/sysext/form/Classes/Mvc/Property/Exception/TypeConverterException.php b/typo3/sysext/form/Classes/Mvc/Property/Exception/TypeConverterException.php
index 9df06b4c873c8453510267ee0153679e06a99be1..c60a10234e8de443eb0af8fc2b2cc19e0aecbad8 100644
--- a/typo3/sysext/form/Classes/Mvc/Property/Exception/TypeConverterException.php
+++ b/typo3/sysext/form/Classes/Mvc/Property/Exception/TypeConverterException.php
@@ -19,7 +19,7 @@ use TYPO3\CMS\Extbase\Error\Error;
 /**
  * A "Type Converter" Exception
  */
-class TypeConverterException extends \TYPO3\CMS\Extbase\Property\Exception\TypeConverterException
+final class TypeConverterException extends \TYPO3\CMS\Extbase\Property\Exception\TypeConverterException
 {
     /**
      * @var Error