diff --git a/src/JobPipeline.php b/src/JobPipeline.php
index 38badf8..9239cda 100644
--- a/src/JobPipeline.php
+++ b/src/JobPipeline.php
@@ -51,7 +51,7 @@ class JobPipeline implements ShouldQueue
         return $this;
     }
 
-    public function shouldBeQueued(bool $shouldBeQueued = true, string $queue = null)
+    public function shouldBeQueued(bool $shouldBeQueued = true, ?string $queue = null)
     {
         $this->shouldBeQueued = $shouldBeQueued;