diff --git a/app/library/Navigation/Container.php b/app/library/Navigation/Container.php
index 5d12dbb..f7a6da7 100644
--- a/app/library/Navigation/Container.php
+++ b/app/library/Navigation/Container.php
@@ -29,7 +29,8 @@ class Container
 
     /**
      * @param $child
-     * @return Node
+     * @return Container
+     * @throws Exception
      */
     public function addChild($child)
     {
@@ -69,7 +70,8 @@ class Container
 
     /**
      * @param $children
-     * @return Node
+     * @return Container
+     * @throws Exception
      */
     public function addChildren($children)
     {
diff --git a/app/library/Navigation/Node.php b/app/library/Navigation/Node.php
index e65d61b..5f9d420 100644
--- a/app/library/Navigation/Node.php
+++ b/app/library/Navigation/Node.php
@@ -56,22 +56,24 @@ class Node extends Container
     protected $_visible = true;
 
     /**
-     * @var Node
+     * Parent container. Null if no parent exists.
+     *
+     * @var Container|null
      */
     protected $_parent = null;
 
     /**
-     * @param $parent
+     * @param Container $parent
      * @return Node
      */
-    public function setParent($parent)
+    public function setParent(Container $parent)
     {
         $this->_parent = $parent;
         return $this;
     }
 
     /**
-     * @return Node
+     * @return Container|null
      */
     public function getParent()
     {