diff --git a/src/Trigger.php b/src/Trigger.php
index f083360..625f7c4 100644
--- a/src/Trigger.php
+++ b/src/Trigger.php
@@ -214,7 +214,7 @@ public function clearCurrent()
     /**
      * Bind events.
      */
-    public function on(string $table, array|string $eventType, array|callable|Closure|string $action = null): void
+    public function on(string $table, array|string $eventType, array|callable|Closure|string|null $action = null): void
     {
         // table as db.tb1,db.tb2,...
         if (str_contains($table, ',')) {
@@ -296,7 +296,7 @@ public function dispatch(EventDTO $event): void
      *
      * @param mixed $events
      */
-    public function fire($events, EventDTO $event = null): void
+    public function fire($events, ?EventDTO $event = null): void
     {
         collect($events)->each(function ($e) use ($event) {
             collect(Arr::get($this->events, $e))->each(fn ($action) => $this->call(...$this->parseAction($action, $event)));