diff --git a/src/ModelInformation/Data/Form/Layout/AbstractModelFormLayoutNodeData.php b/src/ModelInformation/Data/Form/Layout/AbstractModelFormLayoutNodeData.php
index <HASH>..<HASH> 100644
--- a/src/ModelInformation/Data/Form/Layout/AbstractModelFormLayoutNodeData.php
+++ b/src/ModelInformation/Data/Form/Layout/AbstractModelFormLayoutNodeData.php
@@ -61,7 +61,7 @@ class AbstractModelFormLayoutNodeData extends AbstractModelInformationDataObject
      * @param string $key
      * @return mixed|DataObjectInterface
      */
-    public function &getAttributeValue($key)
+    public function &getAttributeValue(string $key)
     {
         if ($key !== 'children') {
             return parent::getAttributeValue($key);
Fixed layout node compatibility with dataobject <I>