protected function upgrade453()
    {
        // Keep track of settings that should be updated.
        $newSettings = array();
        if ($this->get('triggerInvoiceSendEvent') == 2) {
            $newSettings['triggerInvoiceEvent'] = PluginConfig::TriggerInvoiceEvent_Create;
        } else {
            $newSettings['triggerInvoiceEvent'] = PluginConfig::TriggerInvoiceEvent_None;
        }

        return $this->save($newSettings);
    }