diff --git a/Twig/Extension/MarkdownExtension.php b/Twig/Extension/MarkdownExtension.php
index 83c7127..40d52fa 100644
--- a/Twig/Extension/MarkdownExtension.php
+++ b/Twig/Extension/MarkdownExtension.php
@@ -6,7 +6,7 @@ use Michelf\MarkdownExtra;
 
 class MarkdownExtension extends \Twig_Extension
 {
-    private $markdownParser;
+    protected $markdownParser;
 
     public function __construct()
     {