diff --git a/Build/TreeFactory.php b/Build/TreeFactory.php
index b7f29eb..78f4a41 100644
--- a/Build/TreeFactory.php
+++ b/Build/TreeFactory.php
@@ -114,8 +114,10 @@ public function getTree()
             }
 
             if ($this->eventDispatcher) {
-                $this->eventDispatcher->dispatch('webfactory_navigation.tree_initialized',
-                    new TreeInitializedEvent($this->_tree));
+                $this->eventDispatcher->dispatch(
+                    new TreeInitializedEvent($this->_tree),
+                    'webfactory_navigation.tree_initialized'
+                );
             }
         }
 
diff --git a/composer.json b/composer.json
index 19d6a0d..f5f8cc1 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,7 @@
         "symfony/config": "^2.8|^3.4|^4.0",
         "symfony/console": "^2.8|^3.4|^4.0",
         "symfony/dependency-injection": "^3.4|^4.0",
-        "symfony/event-dispatcher": "^2.8|^3.4|^4.0",
+        "symfony/event-dispatcher": "^4.3",
         "symfony/framework-bundle": "^3.4|^4.0",
         "symfony/http-foundation": "^2.8|^3.4|^4.0",
         "symfony/http-kernel": "^2.8|^3.4|^4.0",