diff --git a/Classes/Job/JobManager.php b/Classes/Job/JobManager.php
index f98481e..130c15d 100644
--- a/Classes/Job/JobManager.php
+++ b/Classes/Job/JobManager.php
@@ -123,7 +123,7 @@ public function waitAndExecute(string $queueName, $timeout = null): ?Message
             if (isset($queueSettings['executeIsolated']) && $queueSettings['executeIsolated'] === true) {
                 $messageCacheIdentifier = sha1(serialize($message));
                 $this->messageCache->set($messageCacheIdentifier, $message);
-                Scripts::executeCommand('flowpack.jobqueue.common:job:execute', $this->flowSettings, $queueSettings['outputResults'], ['queue' => $queue->getName(), 'messageCacheIdentifier' => $messageCacheIdentifier]);
+                Scripts::executeCommand('flowpack.jobqueue.common:job:execute', $this->flowSettings, $queueSettings['outputResults'] ?? false, ['queue' => $queue->getName(), 'messageCacheIdentifier' => $messageCacheIdentifier]);
             } else {
                 $this->executeJobForMessage($queue, $message);
             }