diff --git a/classes/tl_nc_message.php b/classes/tl_nc_message.php
index 64f14de0..1a41fed4 100644
--- a/classes/tl_nc_message.php
+++ b/classes/tl_nc_message.php
@@ -130,7 +130,7 @@ public function toggleVisibility($intId, $blnVisible)
         if (is_array($GLOBALS['TL_DCA']['tl_nc_message']['fields']['published']['save_callback'])) {
             foreach ($GLOBALS['TL_DCA']['tl_nc_message']['fields']['published']['save_callback'] as $callback) {
                 if (is_array($callback)) {
-                    $blnVisible = \System::importStatic($callback[0])->$callback[1]($blnVisible, $this);
+                    $blnVisible = \System::importStatic($callback[0])->{$callback[1]}($blnVisible, $this);
                 } elseif (is_callable($callback)) {
                     $blnVisible = $callback($blnVisible, $this);
                 }
diff --git a/composer.json b/composer.json
index f48b2b37..8c803c65 100644
--- a/composer.json
+++ b/composer.json
@@ -3,7 +3,7 @@
     "description":"Notification Center extension for Contao Open Source CMS",
     "keywords":["contao", "notification", "center"],
     "type":"contao-module",
-    "license":"LGPL-3.0+",
+    "license":"LGPL-3.0-or-later",
     "authors":[
         {
             "name":"terminal42 gmbh",
diff --git a/library/NotificationCenter/Gateway/Email.php b/library/NotificationCenter/Gateway/Email.php
index cbcd2820..db628f39 100644
--- a/library/NotificationCenter/Gateway/Email.php
+++ b/library/NotificationCenter/Gateway/Email.php
@@ -70,7 +70,11 @@ public function send(Message $objMessage, array $arrTokens, $strLanguage = '')
 
         // Override SMTP settings if desired
         if (version_compare(VERSION, '4.4', '>=') && $this->objModel->email_overrideSmtp) {
-            $transport = \Swift_SmtpTransport::newInstance($this->objModel->email_smtpHost, $this->objModel->email_smtpPort);
+            if (method_exists(\Swift_SmtpTransport::class, 'newInstance')) {
+                $transport = \Swift_SmtpTransport::newInstance($this->objModel->email_smtpHost, $this->objModel->email_smtpPort);
+            } else {
+                $transport = new \Swift_SmtpTransport($this->objModel->email_smtpHost, $this->objModel->email_smtpPort);
+            }
 
             // Encryption
             if ($this->objModel->email_smtpEnc === 'ssl' || $this->objModel->email_smtpEnc === 'tls') {