diff --git a/core/modules/contextual/contextual.module b/core/modules/contextual/contextual.module
index 2505e77..510a949 100644
--- a/core/modules/contextual/contextual.module
+++ b/core/modules/contextual/contextual.module
@@ -6,16 +6,15 @@
  */
 
 /**
- * Implements hook_custom_theme().
- *
- * @todo Add an event subscriber to the Ajax system to automatically set the
- *   base page theme for all Ajax requests, and then remove this one off.
- *   See http://drupal.org/node/1954892.
+ * Implements hook_menu().
  */
-function contextual_custom_theme() {
-  if (substr(current_path(), 0, 11) === 'contextual/') {
-    return ajax_base_page_theme();
-  }
+function contextual_menu() {
+  $items['contextual/render'] = array(
+    'route_name' => 'contextual_render',
+    'theme callback' => 'ajax_base_page_theme',
+  );
+
+  return $items;
 }
 
 /**
diff --git a/core/modules/edit/edit.module b/core/modules/edit/edit.module
index 5b11560..a07b824 100644
--- a/core/modules/edit/edit.module
+++ b/core/modules/edit/edit.module
@@ -16,15 +16,19 @@
 use Drupal\Component\Utility\NestedArray;
 
 /**
- * Implements hook_custom_theme().
- *
- * @todo Add an event subscriber to the Ajax system to automatically set the
- *   base page theme for all Ajax requests, and then remove this one off.
+ * Implements hook_menu().
  */
-function edit_custom_theme() {
-  if (substr(current_path(), 0, 5) === 'edit/') {
-    return ajax_base_page_theme();
-  }
+function edit_menu() {
+  $items['edit/metadata'] = array(
+    'route_name' => 'edit_metadata',
+    'theme callback' => 'ajax_base_page_theme',
+  );
+  $items['edit/form/%/%/%/%/%'] = array(
+    'route_name' => 'edit_field_form',
+    'theme callback' => 'ajax_base_page_theme',
+  );
+
+  return $items;
 }
 
 /**
diff --git a/core/modules/editor/editor.module b/core/modules/editor/editor.module
index 0f317b9..2d7991d 100644
--- a/core/modules/editor/editor.module
+++ b/core/modules/editor/editor.module
@@ -108,15 +108,15 @@ function editor_library_info() {
 }
 
 /**
- * Implements hook_custom_theme().
- *
- * @todo Add an event subscriber to the Ajax system to automatically set the
- *   base page theme for all Ajax requests, and then remove this one off.
+ * Implements hook_menu().
  */
-function editor_custom_theme() {
-  if (substr(current_path(), 0, 7) === 'editor/') {
-    return ajax_base_page_theme();
-  }
+function editor_menu() {
+  $items['editor/%/%/%/%/%'] = array(
+    'route_name' => 'editor_field_untransformed_text',
+    'theme callback' => 'ajax_base_page_theme',
+  );
+
+  return $items;
 }
 
 /**