diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index 93d905922..9d2194ec6 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -145,7 +145,6 @@ export class ProblemMainHandler extends Handler {
             : await problem.list(
                 domainId, query, sort.length ? 1 : page, limit,
                 quick ? ['title', 'pid', 'domainId', 'docId'] : undefined,
-                this.user._id,
             );
         if (total) {
             pcount = total;
diff --git a/packages/hydrooj/src/model/problem.ts b/packages/hydrooj/src/model/problem.ts
index 2f7dc4a1c..42754ef3e 100644
--- a/packages/hydrooj/src/model/problem.ts
+++ b/packages/hydrooj/src/model/problem.ts
@@ -23,6 +23,7 @@ import {
 import { buildProjection } from '../utils';
 import { PERM, STATUS } from './builtin';
 import * as document from './document';
+import DomainModel from './domain';
 import RecordModel from './record';
 import SolutionModel from './solution';
 import storage from './storage';
@@ -32,9 +33,10 @@ export interface ProblemDoc extends Document { }
 export type Field = keyof ProblemDoc;
 
 const logger = new Logger('problem');
-function sortable(source: string) {
-    const [namespace, pid] = source.includes('-') ? source.split('-') : ['', source];
-    return (namespace ? namespace.padEnd(6, ' ') : '') + pid.replace(/(\d+)/g, (str) => (str.length >= 6 ? str : ('0'.repeat(6 - str.length) + str)));
+function sortable(source: string, namespaces: Record<string, string> = {}) {
+    const [namespace, pid] = source.includes('-') ? source.split('-') : ['default', source];
+    return ((namespaces ? `${namespaces[namespace]}-` : '') + pid)
+        .replace(/(\d+)/g, (str) => (str.length >= 6 ? str : ('0'.repeat(6 - str.length) + str)));
 }
 
 function findOverrideContent(dir: string, base: string) {
@@ -149,8 +151,9 @@ export class ProblemModel {
         content: string, owner: number, tag: string[] = [],
         meta: ProblemCreateOptions = {},
     ) {
+        const ddoc = await DomainModel.get(domainId);
         const args: Partial<ProblemDoc> = {
-            title, tag, hidden: meta.hidden || false, nSubmit: 0, nAccept: 0, sort: sortable(pid || `P${docId}`),
+            title, tag, hidden: meta.hidden || false, nSubmit: 0, nAccept: 0, sort: sortable(pid || `P${docId}`, ddoc?.namespaces),
         };
         if (pid) args.pid = pid;
         if (meta.difficulty) args.difficulty = meta.difficulty;
@@ -171,9 +174,10 @@ export class ProblemModel {
         rawConfig = false,
     ): Promise<ProblemDoc | null> {
         if (Number.isSafeInteger(+pid)) pid = +pid;
+        const ddoc = await DomainModel.get(domainId);
         const res = typeof pid === 'number'
             ? await document.get(domainId, document.TYPE_PROBLEM, pid, projection)
-            : (await document.getMulti(domainId, document.TYPE_PROBLEM, { sort: sortable(pid), pid })
+            : (await document.getMulti(domainId, document.TYPE_PROBLEM, { sort: sortable(pid, ddoc?.namespaces), pid })
                 .project(buildProjection(projection)).limit(1).toArray())[0];
         if (!res) return null;
         try {
@@ -209,11 +213,12 @@ export class ProblemModel {
 
     static async edit(domainId: string, _id: number, $set: Partial<ProblemDoc>): Promise<ProblemDoc> {
         const delpid = $set.pid === '';
+        const ddoc = await DomainModel.get(domainId);
         if (delpid) {
             delete $set.pid;
-            $set.sort = sortable(`P${_id}`);
+            $set.sort = sortable(`P${_id}`, ddoc.namespaces);
         } else if ($set.pid) {
-            $set.sort = sortable($set.pid);
+            $set.sort = sortable($set.pid, ddoc.namespaces);
         }
         await bus.parallel('problem/before-edit', $set);
         const result = await document.set(domainId, document.TYPE_PROBLEM, _id, $set, delpid ? { pid: '' } : undefined);