diff --git a/admin/code/LeftAndMain.php b/admin/code/LeftAndMain.php
index f4a83f10a..041b4c8aa 100644
--- a/admin/code/LeftAndMain.php
+++ b/admin/code/LeftAndMain.php
@@ -1457,7 +1457,7 @@ class LeftAndMain extends Controller implements PermissionProvider
         $id = $request->requestVar('ID');
         $parentID = $request->requestVar('ParentID');
 
-        if ($className == 'SilverStripe\\CMS\\Model\\SiteTree' && $page = DataObject::get_by_id('Page', $id)) {
+        if ($className == 'SilverStripe\\CMS\\Model\\SiteTree' && $page = DataObject::get_by_id(SiteTree::class, $id)) {
             $root = $page->getParentType();
             if (($parentID == '0' || $root == 'root') && !SiteConfig::current_site_config()->canCreateTopLevel()) {
                 $this->getResponse()->setStatusCode(
diff --git a/src/Forms/HTMLEditor/HTMLEditorField_Toolbar.php b/src/Forms/HTMLEditor/HTMLEditorField_Toolbar.php
index 1957e197b..4b3ea01bc 100644
--- a/src/Forms/HTMLEditor/HTMLEditorField_Toolbar.php
+++ b/src/Forms/HTMLEditor/HTMLEditorField_Toolbar.php
@@ -2,9 +2,9 @@
 
 namespace SilverStripe\Forms\HTMLEditor;
 
-use Page;
 use SilverStripe\Assets\File;
 use SilverStripe\Assets\Upload;
+use SilverStripe\CMS\Model\SiteTree;
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\Director;
 use SilverStripe\Control\RequestHandler;
@@ -516,7 +516,7 @@ class HTMLEditorField_Toolbar extends RequestHandler
         $id = (int)$this->getRequest()->getVar('PageID');
         $anchors = array();
 
-        if (($page = Page::get()->byID($id)) && !empty($page)) {
+        if (($page = SiteTree::get()->byID($id)) && !empty($page)) {
             if (!$page->canView()) {
                 throw new HTTPResponse_Exception(
                     _t(
diff --git a/src/Security/Security.php b/src/Security/Security.php
index 09d480a70..7d6910ebe 100644
--- a/src/Security/Security.php
+++ b/src/Security/Security.php
@@ -2,14 +2,16 @@
 
 namespace SilverStripe\Security;
 
+use SilverStripe\CMS\Controllers\ContentController;
+use SilverStripe\CMS\Model\SiteTree;
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\Director;
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Control\HTTPResponse;
 use SilverStripe\Control\Session;
+use SilverStripe\Core\ClassInfo;
 use SilverStripe\Core\Config\Config;
 use SilverStripe\Core\Convert;
-use SilverStripe\Core\ClassInfo;
 use SilverStripe\Core\Injector\Injector;
 use SilverStripe\Dev\Deprecation;
 use SilverStripe\Dev\TestOnly;
@@ -18,16 +20,14 @@ use SilverStripe\Forms\FieldList;
 use SilverStripe\Forms\Form;
 use SilverStripe\Forms\FormAction;
 use SilverStripe\ORM\ArrayList;
-use SilverStripe\ORM\DataObject;
 use SilverStripe\ORM\DB;
+use SilverStripe\ORM\DataObject;
 use SilverStripe\ORM\FieldType\DBField;
 use SilverStripe\ORM\ValidationResult;
 use SilverStripe\View\ArrayData;
 use SilverStripe\View\SSViewer;
 use SilverStripe\View\TemplateGlobalProvider;
 use Exception;
-use Page;
-use Page_Controller;
 use Subsite;
 
 /**
@@ -515,14 +515,14 @@ class Security extends Controller implements TemplateGlobalProvider
         }
 
         // Use sitetree pages to render the security page
-        $tmpPage = new Page();
+        $tmpPage = new SiteTree();
         $tmpPage->Title = $title;
         /** @skipUpgrade */
         $tmpPage->URLSegment = "Security";
         // Disable ID-based caching  of the log-in page by making it a random number
         $tmpPage->ID = -1 * rand(1, 10000000);
 
-        $controller = Page_Controller::create($tmpPage);
+        $controller = ContentController::create($tmpPage);
         $controller->setDataModel($this->model);
         $controller->doInit();
         return $controller;