diff --git a/src/DefinitionResolver.php b/src/DefinitionResolver.php
index a02cb21..6362daf 100644
--- a/src/DefinitionResolver.php
+++ b/src/DefinitionResolver.php
@@ -22,6 +22,11 @@ class DefinitionResolver
      */
     private $typeResolver;
 
+    /**
+     * @var \PhpParser\PrettyPrinterAbstract
+     */
+    private $prettyPrinter;
+
     public function __construct(Project $project)
     {
         $this->project = $project;