diff --git a/src/Adapter/Rest.php b/src/Adapter/Rest.php
index d819884..8912e97 100644
--- a/src/Adapter/Rest.php
+++ b/src/Adapter/Rest.php
@@ -39,7 +39,7 @@ class Rest implements AdapterInterface
 
     public function setup(array $configuration): void
     {
-        $this->auth = AuthenticationEnum::from($configuration['auth'] ?? AuthenticationEnum::Basic->value);
+        $this->auth = AuthenticationEnum::from($configuration['auth'] ?: AuthenticationEnum::Basic->value);
         $this->url = rtrim($configuration['url'], '/');
 
         foreach([ 'username', 'password', 'token', 'headers', 'options' ] as $conf) {