diff --git a/core/tests/Drupal/Tests/DrupalTestBrowser.php b/core/tests/Drupal/Tests/DrupalTestBrowser.php
index 55584b1dc6e987efa5f56da43d5f3614093d8595..5895a30dc3f0438f0c5c17e87470df8a2e087b6e 100644
--- a/core/tests/Drupal/Tests/DrupalTestBrowser.php
+++ b/core/tests/Drupal/Tests/DrupalTestBrowser.php
@@ -80,7 +80,7 @@ public function getClient() {
   /**
    * {@inheritdoc}
    */
-  protected function doRequest($request) {
+  protected function doRequest($request): object {
     $headers = [];
     foreach ($request->getServer() as $key => $val) {
       $key = strtolower(str_replace('_', '-', $key));