diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index 69865ff7f..d5a92136f 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "4.0.7",
+    "version": "4.0.8",
     "bin": "bin/hydrooj.js",
     "main": "src/plugin-api",
     "module": "src/plugin-api",
diff --git a/packages/hydrooj/src/service/server.ts b/packages/hydrooj/src/service/server.ts
index 14d653bf4..25492e0c1 100644
--- a/packages/hydrooj/src/service/server.ts
+++ b/packages/hydrooj/src/service/server.ts
@@ -210,7 +210,7 @@ export class Handler extends HandlerCommon {
 }
 
 async function serial(name: string, ...args: any[]) {
-    const r = await (bus.serial as any)(name, ...args);
+    const r = await (global.app.serial as any)(name, ...args);
     if (r instanceof Error) throw r;
     return r;
 }