diff --git a/Admin/Install/Navigation.install.json b/Admin/Install/Navigation.install.json
index 1be573d..061d47d 100755
--- a/Admin/Install/Navigation.install.json
+++ b/Admin/Install/Navigation.install.json
@@ -63,8 +63,8 @@
                 "pid": "/wiki",
                 "type": 3,
                 "subtype": 1,
-                "name": "Apps",
-                "uri": "{/prefix}wiki/app/list",
+                "name": "Wiki",
+                "uri": "{/prefix}wiki/list",
                 "target": "self",
                 "icon": null,
                 "order": 15,
diff --git a/Admin/Installer.php b/Admin/Installer.php
index b15daec..6662ad9 100755
--- a/Admin/Installer.php
+++ b/Admin/Installer.php
@@ -14,12 +14,15 @@ declare(strict_types=1);
 
 namespace Modules\Knowledgebase\Admin;
 
+use Modules\Knowledgebase\Models\WikiApp;
 use Modules\Knowledgebase\Models\WikiCategory;
 use Modules\Knowledgebase\Models\WikiCategoryMapper;
 use phpOMS\Config\SettingsInterface;
 use phpOMS\DataStorage\Database\DatabasePool;
 use phpOMS\Module\InstallerAbstract;
 use phpOMS\Module\ModuleInfo;
+use Modules\Knowledgebase\Models\WikiAppMapper;
+use Modules\Knowledgebase\Models\NullWikiApp;
 
 /**
  * Installer class.
@@ -38,7 +41,13 @@ final class Installer extends InstallerAbstract
     {
         parent::install($dbPool, $info, $cfgHandler);
 
+        $app = new WikiApp();
+        $app->setName('Default');
+
+        $id = WikiAppMapper::create($app);
+
         $category = new WikiCategory();
+        $category->setApp(new NullWikiApp($id));
         $category->setName('Default');
         $category->setPath('/');
 
diff --git a/Models/WikiCategory.php b/Models/WikiCategory.php
index cb2b77e..32be3c0 100755
--- a/Models/WikiCategory.php
+++ b/Models/WikiCategory.php
@@ -37,10 +37,10 @@ class WikiCategory implements \JsonSerializable
      *
      * There can be different wikis
      *
-     * @var null|WikiApp
+     * @var WikiApp
      * @since 1.0.0
      */
-    private ?WikiApp $app = null;
+    private WikiApp $app;
 
     /**
      * Name.
@@ -66,6 +66,16 @@ class WikiCategory implements \JsonSerializable
      */
     private ?self $parent = null;
 
+    /**
+     * Cosntructor
+     *
+     * @since 1.0.0
+     */
+    public function __construct()
+    {
+        $this->app = new NullWikiApp();
+    }
+
     /**
      * Get id.
      *