diff --git a/_config/extensions.yml b/_config/extensions.yml
index 8d4b0a57..36ece43c 100644
--- a/_config/extensions.yml
+++ b/_config/extensions.yml
@@ -51,10 +51,6 @@ SilverStripe\CMS\Controllers\CMSMain:
     - SilverStripe\Subsites\Extensions\HintsCacheKeyExtension
     - SilverStripe\Subsites\Extensions\SubsiteMenuExtension
 
-SilverStripe\CMS\Controllers\CMSPagesController:
-  extensions:
-    - SilverStripe\Subsites\Extensions\SubsiteMenuExtension
-
 SilverStripe\Subsites\Admin\SubsiteAdmin:
   extensions:
     - SilverStripe\Subsites\Extensions\SubsiteMenuExtension
diff --git a/src/Extensions/LeftAndMainSubsites.php b/src/Extensions/LeftAndMainSubsites.php
index 79c259e4..ba59dda5 100644
--- a/src/Extensions/LeftAndMainSubsites.php
+++ b/src/Extensions/LeftAndMainSubsites.php
@@ -6,7 +6,7 @@
 use SilverStripe\Admin\CMSMenu;
 use SilverStripe\Admin\CMSProfileController;
 use SilverStripe\Admin\LeftAndMain;
-use SilverStripe\CMS\Controllers\CMSPagesController;
+use SilverStripe\CMS\Controllers\CMSMain;
 use SilverStripe\CMS\Model\SiteTree;
 use SilverStripe\CMS\Controllers\CMSPageEditController;
 use SilverStripe\Control\Controller;
@@ -274,22 +274,12 @@ public function alternateAccessCheck(?Member $member = null)
     protected function onBeforeInit()
     {
         $request = Controller::curr()->getRequest();
-        $session = $request->getSession();
-
         $state = SubsiteState::singleton();
 
         // FIRST, check if we need to change subsites due to the URL.
 
         // Catch forced subsite changes that need to cause CMS reloads.
         if ($request->getVar('SubsiteID') !== null) {
-            // Clear current page when subsite changes (or is set for the first time)
-            if ($state->getSubsiteIdWasChanged()) {
-                // sessionNamespace() is protected - see for info
-                $override = $this->owner->config()->get('session_namespace');
-                $sessionNamespace = $override ? $override : get_class($this->owner);
-                $session->clear($sessionNamespace . '.currentPage');
-            }
-
             // Context: Subsite ID has already been set to the state via InitStateMiddleware
 
             // If the user cannot view the current page, redirect to the admin landing section
@@ -306,7 +296,7 @@ protected function onBeforeInit()
                 // will show a list of the requested subsite's pages
                 $currentSubsiteId = $request->getVar('SubsiteID');
                 if ($page && (int) $page->SubsiteID !== (int) $currentSubsiteId) {
-                    return $this->owner->redirect(CMSPagesController::singleton()->Link());
+                    return $this->owner->redirect(CMSMain::singleton()->Link());
                 }
 
                 // Page does belong to the current subsite, so remove the query string parameter and refresh the page
@@ -328,11 +318,11 @@ protected function onBeforeInit()
             && $this->shouldChangeSubsite(
                 get_class($this->owner),
                 $record->SubsiteID,
-                SubsiteState::singleton()->getSubsiteId()
+                $state->getSubsiteId()
             )
         ) {
             // Update current subsite
-            $canViewElsewhere = SubsiteState::singleton()->withState(function ($newState) use ($record) {
+            $canViewElsewhere = $state->withState(function ($newState) use ($record) {
                 $newState->setSubsiteId($record->SubsiteID);
 
                 return (bool) $this->owner->canView(Security::getCurrentUser());
@@ -386,7 +376,7 @@ protected function onBeforeInit()
         return;
     }
 
-    protected function augmentNewSiteTreeItem(&$item)
+    protected function updateNewItem(&$item)
     {
         $request = Controller::curr()->getRequest();
         $item->SubsiteID = $request->postVar('SubsiteID') ?: SubsiteState::singleton()->getSubsiteId();
diff --git a/src/Model/Subsite.php b/src/Model/Subsite.php
index 8ac132fe..a185a110 100644
--- a/src/Model/Subsite.php
+++ b/src/Model/Subsite.php
@@ -728,7 +728,8 @@ public function getPageTypeMap()
     {
         $pageTypeMap = [];
 
-        $pageTypes = SiteTree::page_type_classes();
+        $pageTypes = ClassInfo::getValidSubClasses(SiteTree::class);
+        SiteTree::singleton()->updateAllowedSubClasses($pageTypes);
         foreach ($pageTypes as $pageType) {
             $pageTypeMap[$pageType] = singleton($pageType)->i18n_singular_name();
         }
diff --git a/tests/php/SiteTreeSubsitesTest.php b/tests/php/SiteTreeSubsitesTest.php
index adb65115..b0adca56 100644
--- a/tests/php/SiteTreeSubsitesTest.php
+++ b/tests/php/SiteTreeSubsitesTest.php
@@ -287,7 +287,7 @@ public function testPageTypesBlacklistInCMSMain()
 
         Subsite::changeSubsite($s1);
         $cmsmain = CMSMain::create();
-        $hints = json_decode($cmsmain->SiteTreeHints() ?? '', true);
+        $hints = json_decode($cmsmain->TreeHints() ?? '', true);
         $classes = $hints['Root']['disallowedChildren'];
         $this->assertContains(ErrorPage::class, $classes);
         $this->assertContains(TestClassA::class, $classes);
@@ -298,7 +298,7 @@ public function testPageTypesBlacklistInCMSMain()
         if ($cmsmain->hasMethod('getHintsCache')) {
             $cmsmain->getHintsCache()->clear();
         }
-        $hints = json_decode($cmsmain->SiteTreeHints() ?? '', true);
+        $hints = json_decode($cmsmain->TreeHints() ?? '', true);
 
         $classes = $hints['Root']['disallowedChildren'];
         $this->assertNotContains(ErrorPage::class, $classes);