diff --git a/vendor/league/oauth2-client/src/OptionProvider/PostAuthOptionProvider.php b/vendor/league/oauth2-client/src/OptionProvider/PostAuthOptionProvider.php
index 12d920e..7383fff 100644
--- a/vendor/league/oauth2-client/src/OptionProvider/PostAuthOptionProvider.php
+++ b/vendor/league/oauth2-client/src/OptionProvider/PostAuthOptionProvider.php
@@ -29,10 +29,15 @@ class PostAuthOptionProvider implements OptionProviderInterface
      */
     public function getAccessTokenOptions($method, array $params)
     {
-        $options = ['headers' => ['content-type' => 'application/x-www-form-urlencoded']];
+        $basicAuthCredentials = base64_encode($params['client_id'] .':'.$params['client_secret']);
+
+        $options = ['headers' => ['content-type' => 'application/x-www-form-urlencoded', 'Authorization' => 'Basic '.$basicAuthCredentials]];

         if ($method === AbstractProvider::METHOD_POST) {
-            $options['body'] = $this->getAccessTokenBody($params);
+            $paramsData  = $params;
+            unset($paramsData['client_id']);
+            unset($paramsData['client_secret']);
+            $options['body'] = $this->getAccessTokenBody($paramsData);
         }

         return $options;