diff --git a/Classes/Domain/Validator/SpamShield/SessionMethod.php b/Classes/Domain/Validator/SpamShield/SessionMethod.php
index 5762fdbff..87329ac3f 100644
--- a/Classes/Domain/Validator/SpamShield/SessionMethod.php
+++ b/Classes/Domain/Validator/SpamShield/SessionMethod.php
@@ -21,7 +21,7 @@ public function spamCheck(): bool
             $this->mail->getForm()->getUid(),
             $this->settings
         );
-        $referrer = $this->arguments['__referrer']['@action'];
+        $referrer = $this->arguments['__referrer']['@action'] ?? $this->arguments['action'] ?? '';
         return $referrer !== 'optinConfirm' && $timeFromSession === 0;
     }
 }