diff --git a/framework/yii/helpers/Markdown.php b/framework/yii/helpers/Markdown.php
index 86df045..690df5d 100644
--- a/framework/yii/helpers/Markdown.php
+++ b/framework/yii/helpers/Markdown.php
@@ -24,6 +24,8 @@ namespace yii\helpers;
  * ));
  * ```
  *
+ * Note that in order to use this helper you need to install "michelf/php-markdown" Composer package.
+ *
  * For more details please refer to [PHP Markdown library documentation](http://michelf.ca/projects/php-markdown/).
  * @author Alexander Makarov <sam@rmcreative.ru>
  * @since 2.0