diff --git a/src/PersistentData/Model/OAuthSession.php b/src/PersistentData/Model/OAuthSession.php
index cb442a8..302d60d 100644
--- a/src/PersistentData/Model/OAuthSession.php
+++ b/src/PersistentData/Model/OAuthSession.php
@@ -19,7 +19,7 @@ class OAuthSession extends Model
 
     private array $scope = [];
 
-    private ?string $nonce = '';
+    private ?string $nonce = null;
 
     private ?string $codeChallenge = null;