diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 8a3d0eceae..656afc0fa7 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -2323,7 +2323,9 @@ function install_config_import_batch() {
   // Match up the site UUIDs, the install_base_system install task will have
   // installed the system module and created a new UUID.
   $system_site = $sync->read('system.site');
-  \Drupal::configFactory()->getEditable('system.site')->set('uuid', $system_site['uuid'] ?? NULL)->save();
+  if ($system_site !== FALSE) {
+    \Drupal::configFactory()->getEditable('system.site')->set('uuid', $system_site['uuid'])->save();
+  }
 
   // Create the storage comparer and the config importer.
   $storage_comparer = new StorageComparer($sync, \Drupal::service('config.storage'));
diff --git a/core/lib/Drupal/Core/Security/RequestSanitizer.php b/core/lib/Drupal/Core/Security/RequestSanitizer.php
index 11bd82e517..a778e4be4e 100644
--- a/core/lib/Drupal/Core/Security/RequestSanitizer.php
+++ b/core/lib/Drupal/Core/Security/RequestSanitizer.php
@@ -153,7 +153,7 @@ protected static function checkDestination($destination, array $whitelist) {
   protected static function stripDangerousValues($input, array $whitelist, array &$sanitized_keys) {
     if (is_array($input)) {
       foreach ($input as $key => $value) {
-        if (is_integer($key) || ($key !== '' && $key[0] === '#' && !in_array($key, $whitelist, TRUE))) {
+        if ($key !== '' && ((string) $key)[0] === '#' && !in_array($key, $whitelist, TRUE)) {
           unset($input[$key]);
           $sanitized_keys[] = $key;
         }