diff --git a/Tests/Functional/Mail/MailerHelperTest.php b/Tests/Functional/Mail/MailerHelperTest.php
index 83c0cc1b..e731fc19 100644
--- a/Tests/Functional/Mail/MailerHelperTest.php
+++ b/Tests/Functional/Mail/MailerHelperTest.php
@@ -16,7 +16,10 @@
 
 class MailerHelperTest extends HelperTestCase
 {
-    protected static $class = MailerKernel::class;
+    public static function getKernelClass(): string
+    {
+        return MailerKernel::class;
+    }
 
     public function testSendsEmailUsingMailerComponent()
     {