diff --git a/Debug/TraceableEventDispatcher.php b/Debug/TraceableEventDispatcher.php
index 52e844b..1163e07 100644
--- a/Debug/TraceableEventDispatcher.php
+++ b/Debug/TraceableEventDispatcher.php
@@ -30,8 +30,8 @@
  */
 class TraceableEventDispatcher implements EventDispatcherInterface, ResetInterface
 {
-    protected $logger;
-    protected $stopwatch;
+    protected ?LoggerInterface $logger;
+    protected Stopwatch $stopwatch;
 
     /**
      * @var \SplObjectStorage<WrappedListener, array{string, string}>|null
diff --git a/GenericEvent.php b/GenericEvent.php
index 68a2030..b14faa5 100644
--- a/GenericEvent.php
+++ b/GenericEvent.php
@@ -25,8 +25,8 @@
  */
 class GenericEvent extends Event implements \ArrayAccess, \IteratorAggregate
 {
-    protected $subject;
-    protected $arguments;
+    protected mixed $subject;
+    protected array $arguments;
 
     /**
      * Encapsulate an event with $subject and $args.