diff --git a/HttpServer/Events/OnWorkerError.php b/HttpServer/Events/OnWorkerError.php
index c8a89491..fc29acc5 100644
--- a/HttpServer/Events/OnWorkerError.php
+++ b/HttpServer/Events/OnWorkerError.php
@@ -31,7 +31,7 @@ class OnWorkerError extends Callback
         Event::trigger(Event::SERVER_WORKER_ERROR);
 
         $message = sprintf('Worker#%d::%d error stop. signal %d, exit_code %d, msg %s',
-            $worker_id, $worker_pid, $signal, $exit_code, swoole_strerror(swoole_last_error())
+            $worker_id, $worker_pid, $signal, $exit_code, swoole_strerror(swoole_last_error(), 9)
         );
 
         write($message, 'worker-exit');