diff --git a/src/Exception.php b/src/Exception.php
index 4d24d58..0dd58ca 100644
--- a/src/Exception.php
+++ b/src/Exception.php
@@ -25,7 +25,7 @@ class Exception extends \RuntimeException
      * @param int $code The Exception code
      * @param \Exception $previous The previous exception used for the exception chaining.
      */
-    public function __construct($message = "", $code = 0, \Exception $previous = null)
+    public function __construct($message = "", $code = 0, ?\Exception $previous = null)
     {
         if (!$code) {
             $code = self::E_ANY;
diff --git a/src/TableFormatter.php b/src/TableFormatter.php
index 20d71c6..d952a6e 100644
--- a/src/TableFormatter.php
+++ b/src/TableFormatter.php
@@ -26,7 +26,7 @@ class TableFormatter
      *
      * @param Colors|null $colors
      */
-    public function __construct(Colors $colors = null)
+    public function __construct(?Colors $colors = null)
     {
         // try to get terminal width
         $width = $this->getTerminalWidth();