diff --git a/src/composer.php b/src/composer.php
index 5bf2f2a..94bfe9b 100644
--- a/src/composer.php
+++ b/src/composer.php
@@ -166,9 +166,9 @@ class ezcMailComposer extends ezcMail
     /**
      * Constructs an empty ezcMailComposer object.
      *
-     * @param ezcMailComposerOptions $options
+     * @param ezcMailComposerOptions|null $options
      */
-    public function __construct( ezcMailComposerOptions $options = null )
+    public function __construct( ?ezcMailComposerOptions $options = null )
     {
         $this->properties['plainText'] = null;
         $this->properties['htmlText'] = null;
@@ -298,7 +298,7 @@ public function __isset( $name )
      *            the Mail component. Use addFileAttachment() and
      *            addStringAttachment() instead.
      */
-    public function addAttachment( $fileName, $content = null, $contentType = null, $mimeType = null, ezcMailContentDispositionHeader $contentDisposition = null )
+    public function addAttachment( $fileName, $content = null, $contentType = null, $mimeType = null, ?ezcMailContentDispositionHeader $contentDisposition = null )
     {
         if ( is_null( $content ) )
         {
@@ -330,7 +330,7 @@ public function addAttachment( $fileName, $content = null, $contentType = null,
      * @param string $mimeType
      * @param ezcMailContentDispositionHeader $contentDisposition
      */
-    public function addFileAttachment( $fileName, $contentType = null, $mimeType = null, ezcMailContentDispositionHeader $contentDisposition = null )
+    public function addFileAttachment( $fileName, $contentType = null, $mimeType = null, ?ezcMailContentDispositionHeader $contentDisposition = null )
     {
         if ( is_readable( $fileName ) )
         {
@@ -369,7 +369,7 @@ public function addFileAttachment( $fileName, $contentType = null, $mimeType = n
      * @param string $mimeType
      * @param ezcMailContentDispositionHeader $contentDisposition
      */
-    public function addStringAttachment( $fileName, $content, $contentType = null, $mimeType = null, ezcMailContentDispositionHeader $contentDisposition = null )
+    public function addStringAttachment( $fileName, $content, $contentType = null, $mimeType = null, ?ezcMailContentDispositionHeader $contentDisposition = null )
     {
         $this->attachments[] = array( $fileName, $content, $contentType, $mimeType, $contentDisposition );
     }
diff --git a/src/mail.php b/src/mail.php
index 0e344e4..2414efd 100644
--- a/src/mail.php
+++ b/src/mail.php
@@ -140,7 +140,7 @@ class ezcMail extends ezcMailPart
     /**
      * Constructs an empty ezcMail object.
      */
-    public function __construct( ezcMailOptions $options = null )
+    public function __construct( ?ezcMailOptions $options = null )
     {
         parent::__construct();
 
diff --git a/src/parser/rfc2231_implementation.php b/src/parser/rfc2231_implementation.php
index 985660c..5c1440b 100644
--- a/src/parser/rfc2231_implementation.php
+++ b/src/parser/rfc2231_implementation.php
@@ -137,10 +137,10 @@ public static function parseHeader( $header )
      * will not clear out any old values in the object.
      *
      * @param string $header
-     * @param ezcMailContentDispositionHeader $cd
+     * @param ezcMailContentDispositionHeader|null $cd
      * @return ezcMailContentDispositionHeader
      */
-    public static function parseContentDisposition( $header, ezcMailContentDispositionHeader $cd = null )
+    public static function parseContentDisposition( $header, ?ezcMailContentDispositionHeader $cd = null )
     {
         if ( $cd === null )
         {
diff --git a/src/transports/transport_connection.php b/src/transports/transport_connection.php
index 0f6f048..443648d 100644
--- a/src/transports/transport_connection.php
+++ b/src/transports/transport_connection.php
@@ -75,9 +75,9 @@ class ezcMailTransportConnection
      *         if $options contains a property with a value not allowed
      * @param string $server
      * @param int $port
-     * @param ezcMailTransportOptions $options
+     * @param ezcMailTransportOptions|null $options
      */
-    public function __construct( $server, $port, ezcMailTransportOptions $options = null )
+    public function __construct( $server, $port, ?ezcMailTransportOptions $options = null )
     {
         $errno = null;
         $errstr = null;