diff --git a/composer.json b/composer.json
index 8e3a7c61b..d5bc7d931 100755
--- a/composer.json
+++ b/composer.json
@@ -5,7 +5,7 @@
     "license": "MIT",
     "require": {
         "php" : ">=5.3.0",
-        "swiftmailer/swiftmailer": "~5.2"
+        "swiftmailer/swiftmailer": "~5.2 || ^6.0"
     },
     "require-dev": {
         "psr/log": "*"
diff --git a/lib/mailer/sfMailer.class.php b/lib/mailer/sfMailer.class.php
index ee9ce93e8..86afba3e3 100755
--- a/lib/mailer/sfMailer.class.php
+++ b/lib/mailer/sfMailer.class.php
@@ -239,7 +239,9 @@ public function setDeliveryAddress($address)
    */
   public function compose($from = null, $to = null, $subject = null, $body = null)
   {
-    return Swift_Message::newInstance()
+    $msg = new Swift_Message();
+
+    return $msg
       ->setFrom($from)
       ->setTo($to)
       ->setSubject($subject)
@@ -277,12 +279,12 @@ public function sendNextImmediately()
   /**
    * Sends the given message.
    *
-   * @param Swift_Transport $transport         A transport instance
-   * @param string[]        &$failedRecipients An array of failures by-reference
+   * @param Swift_Mime_Message|Swift_Mime_SimpleMessage $message           The message to send.
+   * @param string[]                                    &$failedRecipients An array of failures by-reference
    *
    * @return int|false The number of sent emails
    */
-  public function send(Swift_Mime_Message $message, &$failedRecipients = null)
+  public function send($message, &$failedRecipients = null)
   {
     if ($this->force)
     {
diff --git a/lib/mailer/sfNoMailer.class.php b/lib/mailer/sfNoMailer.class.php
index 83324e9a0..507b61a33 100644
--- a/lib/mailer/sfNoMailer.class.php
+++ b/lib/mailer/sfNoMailer.class.php
@@ -56,7 +56,7 @@ public function sendNextImmediately()
     return null;
   }
 
-  public function send(Swift_Mime_Message $message, &$failedRecipients = null)
+  public function send($message, &$failedRecipients = null)
   {
     return null;
   }