diff --git a/src/Config.php b/src/Config.php
index fef6cdd..eb661c8 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -8,13 +8,13 @@ class Config implements Contracts\ConfigInterface
 
     protected $config;
 
-    public function __construct($key, $secret, $callbackUri)
+    public function __construct($key, $secret, $callbackUri, array $additionalConfig = [])
     {
-        $this->config = [
+        $this->config = array_merge([
             'client_id' => $key,
             'client_secret' => $secret,
             'redirect' => $callbackUri,
-        ];
+        ], $additionalConfig);
     }
 
     /**