JSon response not detected

case of header =
Array
(
    [0] => application/json; charset=utf-8
)

Author: JLTRY

src/Client.php

@@ -79,6 +79,28 @@ public function __construct($options = [], ?Http $http = null, ?Input $input = n
         $this->application = $application;
     }
 
+    /**
+     * Tests if given response contains JSON header
+     *
+     * @param   Response  $response  The response object
+     *
+     * @return  boolean
+     *
+     */
+    private static function isJsonResponse($response)
+    {
+        foreach (['Content-Type', 'content-type'] as $type) {
+            if (array_key_exists($type, $response->headers)) {
+                $content_type =  is_array($response->headers[$type]) ?
+                                    $response->headers[$type][0] : $response->headers[$type];
+                if (strpos($content_type, 'application/json') !== false) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
     /**
      * Get the access token or redirect to the authentication URL.
      *
@@ -112,7 +134,7 @@ public function authenticate()
                 );
             }
 
-            if (in_array('application/json', $response->getHeader('Content-Type'))) {
+            if ($this->isJsonResponse($response)) {
                 $token = array_merge(json_decode($response->body, true), ['created' => time()]);
             } else {
                 parse_str($response->body, $token);