diff --git a/README.md b/README.md
index bfe8dae..207c7e1 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,11 @@ This library is used by https://poser.pugx.org
 [![Latest Stable Version](https://poser.pugx.org/badges/poser/version.svg)](https://packagist.org/packages/badges/poser) [![Latest Unstable Version](https://poser.pugx.org/badges/poser/v/unstable.svg)](//packagist.org/packages/badges/poser) [![Total Downloads](https://poser.pugx.org/badges/poser/downloads.svg)](https://packagist.org/packages/badges/poser)
 [![Build Status](https://travis-ci.org/badges/poser.svg?branch=master)](https://travis-ci.org/badges/poser)
 
+## Dependencies
+
+* PHP 5.3 or higher
+* GD extension
+
 ## Use as command
 
 #### 1. Create a project
diff --git a/composer.json b/composer.json
index 1185b5e..3d4da52 100644
--- a/composer.json
+++ b/composer.json
@@ -24,6 +24,7 @@
     },
     "require": {
         "php": ">=5.3",
+        "ext-gd": "*",
         "symfony/console": "~2.0|~3.0",
         "coduo/phpspec-data-provider-extension": "^1.0"
     },