diff --git a/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php b/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php
index 7d25cd5735..4ed900e1fb 100644
--- a/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php
+++ b/src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php
@@ -39,7 +39,13 @@ class SendMessageMiddleware implements MiddlewareInterface
     public function __construct(SendersLocatorInterface $sendersLocator, EventDispatcherInterface $eventDispatcher = null)
     {
         $this->sendersLocator = $sendersLocator;
-        $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+
+        if (null !== $eventDispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+        } else {
+            $this->eventDispatcher = $eventDispatcher;
+        }
+
         $this->logger = new NullLogger();
     }
 
diff --git a/src/Symfony/Component/Messenger/Worker.php b/src/Symfony/Component/Messenger/Worker.php
index 6205baefd4..fbd8e56f42 100644
--- a/src/Symfony/Component/Messenger/Worker.php
+++ b/src/Symfony/Component/Messenger/Worker.php
@@ -52,7 +52,13 @@ class Worker implements WorkerInterface
         $this->receivers = $receivers;
         $this->bus = $bus;
         $this->retryStrategies = $retryStrategies;
-        $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+
+        if (null !== $eventDispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+        } else {
+            $this->eventDispatcher = $eventDispatcher;
+        }
+
         $this->logger = $logger;
     }
 
diff --git a/src/Symfony/Component/Security/Core/Authorization/Voter/TraceableVoter.php b/src/Symfony/Component/Security/Core/Authorization/Voter/TraceableVoter.php
index e5ce1f696b..81ec62c146 100644
--- a/src/Symfony/Component/Security/Core/Authorization/Voter/TraceableVoter.php
+++ b/src/Symfony/Component/Security/Core/Authorization/Voter/TraceableVoter.php
@@ -31,7 +31,12 @@ class TraceableVoter implements VoterInterface
     public function __construct(VoterInterface $voter, EventDispatcherInterface $eventDispatcher)
     {
         $this->voter = $voter;
-        $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+
+        if (class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+        } else {
+            $this->eventDispatcher = $eventDispatcher;
+        }
     }
 
     public function vote(TokenInterface $token, $subject, array $attributes)
diff --git a/src/Symfony/Component/Security/Guard/GuardAuthenticatorHandler.php b/src/Symfony/Component/Security/Guard/GuardAuthenticatorHandler.php
index b39d9b2700..39a102015f 100644
--- a/src/Symfony/Component/Security/Guard/GuardAuthenticatorHandler.php
+++ b/src/Symfony/Component/Security/Guard/GuardAuthenticatorHandler.php
@@ -46,7 +46,13 @@ class GuardAuthenticatorHandler
     public function __construct(TokenStorageInterface $tokenStorage, EventDispatcherInterface $eventDispatcher = null, array $statelessProviderKeys = [])
     {
         $this->tokenStorage = $tokenStorage;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+
+        if (null !== $eventDispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+        } else {
+            $this->dispatcher = $eventDispatcher;
+        }
+
         $this->statelessProviderKeys = $statelessProviderKeys;
     }
 
diff --git a/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php b/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php
index 6b35899073..1929e4cfc3 100644
--- a/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/AbstractAuthenticationListener.php
@@ -93,7 +93,13 @@ abstract class AbstractAuthenticationListener implements ListenerInterface
             'require_previous_session' => true,
         ], $options);
         $this->logger = $logger;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
+
         $this->httpUtils = $httpUtils;
     }
 
diff --git a/src/Symfony/Component/Security/Http/Firewall/AbstractPreAuthenticatedListener.php b/src/Symfony/Component/Security/Http/Firewall/AbstractPreAuthenticatedListener.php
index 500ae43e49..6a3f1377c7 100644
--- a/src/Symfony/Component/Security/Http/Firewall/AbstractPreAuthenticatedListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/AbstractPreAuthenticatedListener.php
@@ -52,7 +52,12 @@ abstract class AbstractPreAuthenticatedListener implements ListenerInterface
         $this->authenticationManager = $authenticationManager;
         $this->providerKey = $providerKey;
         $this->logger = $logger;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
     }
 
     /**
diff --git a/src/Symfony/Component/Security/Http/Firewall/ContextListener.php b/src/Symfony/Component/Security/Http/Firewall/ContextListener.php
index 1059dd6c5d..26b6239ab3 100644
--- a/src/Symfony/Component/Security/Http/Firewall/ContextListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/ContextListener.php
@@ -66,7 +66,13 @@ class ContextListener implements ListenerInterface
         $this->userProviders = $userProviders;
         $this->sessionKey = '_security_'.$contextKey;
         $this->logger = $logger;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
+
         $this->trustResolver = $trustResolver ?: new AuthenticationTrustResolver(AnonymousToken::class, RememberMeToken::class);
     }
 
diff --git a/src/Symfony/Component/Security/Http/Firewall/RememberMeListener.php b/src/Symfony/Component/Security/Http/Firewall/RememberMeListener.php
index ebc03db862..78841ecce0 100644
--- a/src/Symfony/Component/Security/Http/Firewall/RememberMeListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/RememberMeListener.php
@@ -49,7 +49,13 @@ class RememberMeListener implements ListenerInterface
         $this->rememberMeServices = $rememberMeServices;
         $this->authenticationManager = $authenticationManager;
         $this->logger = $logger;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
+
         $this->catchExceptions = $catchExceptions;
         $this->sessionStrategy = null === $sessionStrategy ? new SessionAuthenticationStrategy(SessionAuthenticationStrategy::MIGRATE) : $sessionStrategy;
     }
diff --git a/src/Symfony/Component/Security/Http/Firewall/SimplePreAuthenticationListener.php b/src/Symfony/Component/Security/Http/Firewall/SimplePreAuthenticationListener.php
index 2c444e823b..69f773269c 100644
--- a/src/Symfony/Component/Security/Http/Firewall/SimplePreAuthenticationListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/SimplePreAuthenticationListener.php
@@ -65,7 +65,13 @@ class SimplePreAuthenticationListener implements ListenerInterface
         $this->providerKey = $providerKey;
         $this->simpleAuthenticator = $simpleAuthenticator;
         $this->logger = $logger;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
+
         $this->trustResolver = $trustResolver ?: new AuthenticationTrustResolver(AnonymousToken::class, RememberMeToken::class);
     }
 
diff --git a/src/Symfony/Component/Security/Http/Firewall/SwitchUserListener.php b/src/Symfony/Component/Security/Http/Firewall/SwitchUserListener.php
index 4b82fa1f8c..f605a279aa 100644
--- a/src/Symfony/Component/Security/Http/Firewall/SwitchUserListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/SwitchUserListener.php
@@ -70,7 +70,13 @@ class SwitchUserListener implements ListenerInterface
         $this->usernameParameter = $usernameParameter;
         $this->role = $role;
         $this->logger = $logger;
-        $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
+
         $this->stateless = $stateless;
     }
 
diff --git a/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php b/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php
index 8606899a7e..7089c89dcb 100644
--- a/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php
@@ -69,7 +69,13 @@ class UsernamePasswordJsonAuthenticationListener implements ListenerInterface
         $this->successHandler = $successHandler;
         $this->failureHandler = $failureHandler;
         $this->logger = $logger;
-        $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+
+        if (null !== $eventDispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->eventDispatcher = LegacyEventDispatcherProxy::decorate($eventDispatcher);
+        } else {
+            $this->eventDispatcher = $eventDispatcher;
+        }
+
         $this->options = array_merge(['username_path' => 'username', 'password_path' => 'password'], $options);
         $this->propertyAccessor = $propertyAccessor ?: PropertyAccess::createPropertyAccessor();
     }
diff --git a/src/Symfony/Component/Workflow/Workflow.php b/src/Symfony/Component/Workflow/Workflow.php
index 53fef69274..625086b2f1 100644
--- a/src/Symfony/Component/Workflow/Workflow.php
+++ b/src/Symfony/Component/Workflow/Workflow.php
@@ -43,7 +43,13 @@ class Workflow implements WorkflowInterface
     {
         $this->definition = $definition;
         $this->markingStore = $markingStore ?: new MultipleStateMarkingStore();
-        $this->dispatcher = null !== $dispatcher ? LegacyEventDispatcherProxy::decorate($dispatcher) : null;
+
+        if (null !== $dispatcher && class_exists(LegacyEventDispatcherProxy::class)) {
+            $this->dispatcher = LegacyEventDispatcherProxy::decorate($dispatcher);
+        } else {
+            $this->dispatcher = $dispatcher;
+        }
+
         $this->name = $name;
     }