diff --git a/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php
index 04fe435..199ac09 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php
@@ -213,7 +213,7 @@ public function testPatchDxForSecuritySensitiveBaseFields() {
       RequestOptions::HEADERS => [],
       RequestOptions::BODY => $this->serializer->encode($request_body, 'json'),
     ];
-    $response = $this->httpClient->request('POST', Url::fromRoute('user.login.http')->setRouteParameter('_format', 'json')->toString(), $request_options);
+    $response = $this->request('POST', Url::fromRoute('user.login.http')->setRouteParameter('_format', 'json'), $request_options);
     $this->assertSame(200, $response->getStatusCode());
   }
 
diff --git a/core/modules/rest/tests/src/Functional/ResourceTestBase.php b/core/modules/rest/tests/src/Functional/ResourceTestBase.php
index c346157..c9e4c44 100644
--- a/core/modules/rest/tests/src/Functional/ResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/ResourceTestBase.php
@@ -94,11 +94,6 @@
   public static $modules = ['rest'];
 
   /**
-   * @var \GuzzleHttp\ClientInterface
-   */
-  protected $httpClient;
-
-  /**
    * {@inheritdoc}
    */
   public function setUp() {
@@ -135,10 +130,6 @@ public function setUp() {
     // Ensure there's a clean slate: delete all REST resource config entities.
     $this->resourceConfigStorage->delete($this->resourceConfigStorage->loadMultiple());
     $this->refreshTestStateAfterRestConfigChange();
-
-    // Set up a HTTP client that accepts relative URLs.
-    $this->httpClient = $this->container->get('http_client_factory')
-      ->fromOptions(['base_uri' => $this->baseUrl]);
   }
 
   /**
@@ -344,7 +335,8 @@ protected function grantPermissionsToTestedRole(array $permissions) {
   protected function request($method, Url $url, array $request_options) {
     $request_options[RequestOptions::HTTP_ERRORS] = FALSE;
     $request_options = $this->decorateWithXdebugCookie($request_options);
-    return $this->httpClient->request($method, $url->toString(), $request_options);
+    $client = $this->getSession()->getDriver()->getClient()->getClient();
+    return $client->request($method, $url->setAbsolute(TRUE)->toString(), $request_options);
   }
 
   /**