Neos\Flow\Persistence\Generic\PersistenceManager::update PHP Method

    public function update($object)
    {
        if ($this->isNewObject($object)) {
            throw new UnknownObjectException('The object of type "' . get_class($object) . '" given to update must be persisted already, but is new.', 1249479819);
        }
        $this->hasUnpersistedChanges = true;
        $this->changedObjects->attach($object);
    }