diff --git a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php
index 471f820c2199b..58cb40b39e432 100644
--- a/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php
+++ b/src/Symfony/Bundle/SecurityBundle/DependencyInjection/SecurityExtension.php
@@ -681,7 +681,7 @@ private function createExceptionListener(ContainerBuilder $container, array $con
         return $exceptionListenerId;
     }
 
-    private function createSwitchUserListener(ContainerBuilder $container, string $id, array $config, string $defaultProvider, bool $stateless): string
+    private function createSwitchUserListener(ContainerBuilder $container, string $id, array $config, ?string $defaultProvider, bool $stateless): string
     {
         $userProvider = isset($config['provider']) ? $this->getUserProviderId($config['provider']) : $defaultProvider;
 
diff --git a/src/Symfony/Bundle/SecurityBundle/Tests/DependencyInjection/SecurityExtensionTest.php b/src/Symfony/Bundle/SecurityBundle/Tests/DependencyInjection/SecurityExtensionTest.php
index 7c84f953a55d8..35a1930158235 100644
--- a/src/Symfony/Bundle/SecurityBundle/Tests/DependencyInjection/SecurityExtensionTest.php
+++ b/src/Symfony/Bundle/SecurityBundle/Tests/DependencyInjection/SecurityExtensionTest.php
@@ -390,6 +390,30 @@ public function sessionConfigurationProvider()
         ];
     }
 
+    public function testSwitchUserWithSeveralDefinedProvidersButNoFirewallRootProviderConfigured()
+    {
+        $container = $this->getRawContainer();
+        $container->loadFromExtension('security', [
+            'providers' => [
+                'first' => ['id' => 'foo'],
+                'second' => ['id' => 'bar'],
+            ],
+
+            'firewalls' => [
+                'foobar' => [
+                    'switch_user' => [
+                        'provider' => 'second',
+                    ],
+                    'anonymous' => true,
+                ],
+            ],
+        ]);
+
+        $container->compile();
+
+        $this->assertEquals(new Reference('security.user.provider.concrete.second'), $container->getDefinition('security.authentication.switchuser_listener.foobar')->getArgument(1));
+    }
+
     protected function getRawContainer()
     {
         $container = new ContainerBuilder();