diff --git a/library/Businessprocess/Node.php b/library/Businessprocess/Node.php
index 836f62b..0510859 100644
--- a/library/Businessprocess/Node.php
+++ b/library/Businessprocess/Node.php
@@ -74,7 +74,7 @@ abstract class Node
     /**
      * Node state
      *
-     * @var int
+     * @var ?int
      */
     protected $state;