diff --git a/Classes/Domain/Validator/SpamShield/ValueBlacklistMethod.php b/Classes/Domain/Validator/SpamShield/ValueBlacklistMethod.php
index fa238e82f..3f5c0b7fc 100644
--- a/Classes/Domain/Validator/SpamShield/ValueBlacklistMethod.php
+++ b/Classes/Domain/Validator/SpamShield/ValueBlacklistMethod.php
@@ -28,7 +28,10 @@ public function spamCheck(): bool
                 continue;
             }
             foreach ($this->getValues() as $blackword) {
-                if ($this->isStringInString($answer->getValue(), $blackword)) {
+                if (is_bool($answer->getValue())) {
+                    continue;   
+                }
+                if ($this->isStringInString((string)$answer->getValue(), $blackword)) {
                     return true;
                 }
             }