diff --git a/src/Symfony/Component/HttpClient/MockHttpClient.php b/src/Symfony/Component/HttpClient/MockHttpClient.php
index a794faff6e75c..538243f56c85d 100644
--- a/src/Symfony/Component/HttpClient/MockHttpClient.php
+++ b/src/Symfony/Component/HttpClient/MockHttpClient.php
@@ -34,7 +34,7 @@ class MockHttpClient implements HttpClientInterface
     /**
      * @param callable|callable[]|ResponseInterface|ResponseInterface[]|iterable|null $responseFactory
      */
-    public function __construct($responseFactory = null, string $baseUri = null)
+    public function __construct($responseFactory = null, ?string $baseUri = 'https://example.com')
     {
         if ($responseFactory instanceof ResponseInterface) {
             $responseFactory = [$responseFactory];
diff --git a/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php b/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php
index 33ddccd7827c3..e1ce32bc70fa4 100644
--- a/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/MockHttpClientTest.php
@@ -27,7 +27,7 @@ class MockHttpClientTest extends HttpClientTestCase
      */
     public function testMocking($factory, array $expectedResponses)
     {
-        $client = new MockHttpClient($factory, 'https://example.com/');
+        $client = new MockHttpClient($factory);
         $this->assertSame(0, $client->getRequestsCount());
 
         $urls = ['/foo', '/bar'];
@@ -126,7 +126,7 @@ public function validResponseFactoryProvider()
      */
     public function testTransportExceptionThrowsIfPerformedMoreRequestsThanConfigured($factory)
     {
-        $client = new MockHttpClient($factory, 'https://example.com/');
+        $client = new MockHttpClient($factory);
 
         $client->request('POST', '/foo');
         $client->request('POST', '/foo');
diff --git a/src/Symfony/Component/HttpClient/Tests/ScopingHttpClientTest.php b/src/Symfony/Component/HttpClient/Tests/ScopingHttpClientTest.php
index bfca02b3581aa..078475bf1010c 100644
--- a/src/Symfony/Component/HttpClient/Tests/ScopingHttpClientTest.php
+++ b/src/Symfony/Component/HttpClient/Tests/ScopingHttpClientTest.php
@@ -91,7 +91,7 @@ public function testMatchingUrlsAndOptions()
 
     public function testForBaseUri()
     {
-        $client = ScopingHttpClient::forBaseUri(new MockHttpClient(), 'http://example.com/foo');
+        $client = ScopingHttpClient::forBaseUri(new MockHttpClient(null, null), 'http://example.com/foo');
 
         $response = $client->request('GET', '/bar');
         $this->assertSame('http://example.com/foo', implode('', $response->getRequestOptions()['base_uri']));