diff --git a/lib/ext/Syncroton/Registry.php b/lib/ext/Syncroton/Registry.php
--- a/lib/ext/Syncroton/Registry.php
+++ b/lib/ext/Syncroton/Registry.php
@@ -526,7 +526,7 @@
      */
     public function offsetExists($index)
     {
-        return array_key_exists($index, $this);
+        return property_exists($index, $this);
     }
 
 }