diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index f59dd468c..d8257997e 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.13.53",
+    "version": "2.13.54",
     "bin": "bin/hydrooj.js",
     "main": "dist/loader.js",
     "typings": "dist/loader.d.ts",
diff --git a/packages/hydrooj/src/model/problem.ts b/packages/hydrooj/src/model/problem.ts
index f40e59528..647d2b595 100644
--- a/packages/hydrooj/src/model/problem.ts
+++ b/packages/hydrooj/src/model/problem.ts
@@ -82,7 +82,6 @@ export async function add(
     tag: string[] = [], category: string[] = [], data: ProblemDataSource = null, hidden = false,
 ) {
     const pidCounter = await domain.inc(domainId, 'pidCounter', 1);
-    if (!pid) pid = pidCounter.toString();
     return await document.add(
         domainId, content, owner, document.TYPE_PROBLEM, pidCounter, null, null,
         {
diff --git a/packages/hydrooj/src/upgrade.ts b/packages/hydrooj/src/upgrade.ts
index aeee7bf40..e745a0d69 100644
--- a/packages/hydrooj/src/upgrade.ts
+++ b/packages/hydrooj/src/upgrade.ts
@@ -1,6 +1,7 @@
 /* eslint-disable no-await-in-loop */
 import * as domain from './model/domain';
 import * as document from './model/document';
+import { db } from './service/db';
 
 type UpgradeScript = () => Promise<void>;
 
@@ -29,6 +30,9 @@ const scripts: UpgradeScript[] = [
             if (bulk.length) await bulk.execute();
         }
     },
+    async function _2_3() {
+        await db.collection('document').updateMany({ pid: /^\d+$/i }, { $unset: { pid: '' } });
+    },
 ];
 
 export = scripts;