diff --git a/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php b/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php
index d13b192c5b39..79ca524f2def 100644
--- a/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php
+++ b/src/Symfony/Contracts/HttpClient/Test/HttpClientTestCase.php
@@ -26,7 +26,7 @@ abstract class HttpClientTestCase extends TestCase
 {
     private static $server;
 
-    public static function setUpBeforeClass()
+    public static function setUpBeforeClass(): void
     {
         TestHttpServer::start();
     }