diff --git a/src/Events.php b/src/Events.php
index 3405086..4b87f01 100644
--- a/src/Events.php
+++ b/src/Events.php
@@ -50,7 +50,7 @@ protected function assertValidEvent($event)
      * @param string $event
      * @return bool
      */
-    public function isValidEvent($event)
+    public function isValidEvent(string $event): bool
     {
         return true;
     }