diff --git a/src/RabbitQueue.php b/src/RabbitQueue.php
index 9310475..f49e8c8 100644
--- a/src/RabbitQueue.php
+++ b/src/RabbitQueue.php
@@ -157,7 +157,7 @@ public function pop($queue = null)
         return null;
     }
 
-    public function getQueue(string $queue = null): string
+    public function getQueue(?string $queue = null): string
     {
         return $queue ?? $this->defaultQueue;
     }