diff --git a/src/Support/ScheduledTasks/Tasks/Task.php b/src/Support/ScheduledTasks/Tasks/Task.php
index 1f783a3..7fa09dd 100644
--- a/src/Support/ScheduledTasks/Tasks/Task.php
+++ b/src/Support/ScheduledTasks/Tasks/Task.php
@@ -99,7 +99,7 @@ public function previousRunAt(): CarbonInterface
         return Date::instance($dateTime);
     }
 
-    public function nextRunAt(CarbonInterface $now = null): CarbonInterface
+    public function nextRunAt(?CarbonInterface $now = null): CarbonInterface
     {
         $dateTime = CronExpression::factory($this->cronExpression())->getNextRunDate(
             $now ?? now(),