diff --git a/core/lib/Drupal/Core/Ajax/AjaxResponseAttachmentsProcessor.php b/core/lib/Drupal/Core/Ajax/AjaxResponseAttachmentsProcessor.php
index 45aa45e..e2382b5 100644
--- a/core/lib/Drupal/Core/Ajax/AjaxResponseAttachmentsProcessor.php
+++ b/core/lib/Drupal/Core/Ajax/AjaxResponseAttachmentsProcessor.php
@@ -128,7 +128,7 @@ public function processAttachments(AttachmentsInterface $response) {
    *   An array of commands ready to be returned as JSON.
    */
   protected function buildAttachmentsCommands(AjaxResponse $response, Request $request) {
-    $ajax_page_state = $request->request->get('ajax_page_state');
+    $ajax_page_state = $request->query->get('ajax_page_state') ?: $request->request->get('ajax_page_state');
 
     // Aggregate CSS/JS if necessary, but only during normal site operation.
     $optimize_css = !defined('MAINTENANCE_MODE') && $this->config->get('css.preprocess');
diff --git a/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php b/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
index 2f9aeb3..1d17f50 100644
--- a/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
+++ b/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php
@@ -156,7 +156,7 @@ public function processAttachments(AttachmentsInterface $response) {
       // Take Ajax page state into account, to allow for something like
       // Turbolinks to be implemented without altering core.
       // @see https://github.com/rails/turbolinks/
-      $ajax_page_state = $this->requestStack->getCurrentRequest()->get('ajax_page_state');
+      $ajax_page_state = $this->requestStack->getCurrentRequest()->query->get('ajax_page_state') ?: $this->requestStack->getCurrentRequest()->request->get('ajax_page_state');
       $assets->setAlreadyLoadedLibraries(isset($ajax_page_state) ? explode(',', $ajax_page_state['libraries']) : []);
       $variables = $this->processAssetLibraries($assets, $attachment_placeholders);
       // $variables now contains the markup to load the asset libraries. Update
diff --git a/core/lib/Drupal/Core/Theme/AjaxBasePageNegotiator.php b/core/lib/Drupal/Core/Theme/AjaxBasePageNegotiator.php
index 5cd2ee3..c761d3b 100644
--- a/core/lib/Drupal/Core/Theme/AjaxBasePageNegotiator.php
+++ b/core/lib/Drupal/Core/Theme/AjaxBasePageNegotiator.php
@@ -65,7 +65,7 @@ public function __construct(CsrfTokenGenerator $token_generator, ConfigFactoryIn
    * {@inheritdoc}
    */
   public function applies(RouteMatchInterface $route_match) {
-    $ajax_page_state = $this->requestStack->getCurrentRequest()->request->get('ajax_page_state');
+    $ajax_page_state = $this->requestStack->getCurrentRequest()->query->get('ajax_page_state') ?: $this->requestStack->getCurrentRequest()->request->get('ajax_page_state');
     return !empty($ajax_page_state['theme']) && isset($ajax_page_state['theme_token']);
   }
 
@@ -73,7 +73,7 @@ public function applies(RouteMatchInterface $route_match) {
    * {@inheritdoc}
    */
   public function determineActiveTheme(RouteMatchInterface $route_match) {
-    $ajax_page_state = $this->requestStack->getCurrentRequest()->request->get('ajax_page_state');
+    $ajax_page_state = $this->requestStack->getCurrentRequest()->query->get('ajax_page_state') ?: $this->requestStack->getCurrentRequest()->request->get('ajax_page_state');
     $theme = $ajax_page_state['theme'];
     $token = $ajax_page_state['theme_token'];
 
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index fefe9f3..485ea26 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -511,7 +511,7 @@
         }
       },
       dataType: 'json',
-      type: 'POST'
+      type: typeof ajax.type !== 'undefined' ? ajax.type : 'POST'
     };
 
     if (element_settings.dialog) {