diff --git a/src/NodeVisitor/ReferencesCollector.php b/src/NodeVisitor/ReferencesCollector.php
index 7e35beb..ae3027e 100644
--- a/src/NodeVisitor/ReferencesCollector.php
+++ b/src/NodeVisitor/ReferencesCollector.php
@@ -19,6 +19,11 @@ class ReferencesCollector extends NodeVisitorAbstract
      */
     public $nodes = [];
 
+    /**
+     * @var DefinitionResolver
+     */
+    private $definitionResolver;
+
     /**
      * @param DefinitionResolver $definitionResolver The DefinitionResolver to resolve reference nodes to definitions
      */