diff --git a/lib/Assert/InvalidArgumentException.php b/lib/Assert/InvalidArgumentException.php
index 20c89099..c76951e0 100644
--- a/lib/Assert/InvalidArgumentException.php
+++ b/lib/Assert/InvalidArgumentException.php
@@ -36,7 +36,7 @@ public function __construct($message, $code, $propertyPath, $value, array $const
      * Useful to transport information about the nature of the error
      * back to higher layers.
      *
-     * @return string
+     * @return string|null
      */
     public function getPropertyPath()
     {