diff --git a/packages/hydrooj/src/handler/contest.ts b/packages/hydrooj/src/handler/contest.ts
index d69334a9..1cdc4ccd 100644
--- a/packages/hydrooj/src/handler/contest.ts
+++ b/packages/hydrooj/src/handler/contest.ts
@@ -385,12 +385,12 @@ export class ContestEditHandler extends Handler {
     @param('pids', Types.Content)
     @param('rated', Types.Boolean)
     @param('code', Types.String, true)
-    @param('autoHide', Types.Boolean, true)
+    @param('autoHide', Types.Boolean)
     @param('assign', Types.CommaSeperatedArray, true)
     @param('lock', Types.UnsignedInt, true)
     @param('contestDuration', Types.Float, true)
     @param('maintainer', Types.NumericArray, true)
-    @param('allowViewCode', Types.Boolean, true)
+    @param('allowViewCode', Types.Boolean)
     async postUpdate(
         domainId: string, tid: ObjectID, beginAtDate: string, beginAtTime: string, duration: number,
         title: string, content: string, rule: string, _pids: string, rated = false,
diff --git a/packages/hydrooj/src/handler/discussion.ts b/packages/hydrooj/src/handler/discussion.ts
index 7f5bc451..ebc90ef8 100644
--- a/packages/hydrooj/src/handler/discussion.ts
+++ b/packages/hydrooj/src/handler/discussion.ts
@@ -358,7 +358,7 @@ class DiscussionRawHandler extends DiscussionHandler {
     @param('drid', Types.ObjectID, true)
     @param('drrid', Types.ObjectID, true)
     @param('time', Types.UnsignedInt, true)
-    @param('all', Types.Boolean, true)
+    @param('all', Types.Boolean)
     async get(domainId: string, did: ObjectID, drid: ObjectID, drrid: ObjectID, ts: number, all = false) {
         if (all) {
             this.response.body.history = await discussion.getHistory(domainId, drrid || drid || did);
diff --git a/packages/hydrooj/src/handler/manage.ts b/packages/hydrooj/src/handler/manage.ts
index 007a3898..cfa7cdba 100644
--- a/packages/hydrooj/src/handler/manage.ts
+++ b/packages/hydrooj/src/handler/manage.ts
@@ -297,7 +297,7 @@ class SystemUserPrivHandler extends SystemHandler {
     @requireSudo
     @param('uid', Types.Int)
     @param('priv', Types.UnsignedInt)
-    @param('system', Types.Boolean, true)
+    @param('system', Types.Boolean)
     async post(domainId: string, uid: number, priv: number, editSystem: boolean) {
         if (!editSystem) {
             const udoc = await user.getById(domainId, uid);
diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index c1955678..b7fcbc79 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -379,7 +379,7 @@ export class ProblemDetailHandler extends ContestDetailBaseHandler {
     }
 
     @query('tid', Types.ObjectID, true)
-    @query('pjax', Types.Boolean, true)
+    @query('pjax', Types.Boolean)
     async get(...args: any[]) {
         // Navigate to current additional file download
         // e.g. ![img](a.jpg) will navigate to ![img](./pid/file/a.jpg)
diff --git a/packages/hydrooj/src/handler/record.ts b/packages/hydrooj/src/handler/record.ts
index 1c83334a..ea5b9b40 100644
--- a/packages/hydrooj/src/handler/record.ts
+++ b/packages/hydrooj/src/handler/record.ts
@@ -32,7 +32,7 @@ class RecordListHandler extends ContestDetailBaseHandler {
     @param('lang', Types.String, true)
     @param('status', Types.Int, true)
     @param('fullStatus', Types.Boolean)
-    @param('allDomain', Types.Boolean, true)
+    @param('allDomain', Types.Boolean)
     async get(
         domainId: string, page = 1, pid?: string | number, tid?: ObjectID,
         uidOrName?: string, lang?: string, status?: number, full = false,
diff --git a/packages/hydrooj/src/lib/validator.ts b/packages/hydrooj/src/lib/validator.ts
index 7875671e..9aca2d1d 100644
--- a/packages/hydrooj/src/lib/validator.ts
+++ b/packages/hydrooj/src/lib/validator.ts
@@ -8,7 +8,7 @@ import saslprep from 'saslprep';
 type InputType = string | number | Record<string, any> | any[];
 export type Converter<T> = (value: any) => T;
 export type Validator<Loose extends boolean = true> = (value: Loose extends true ? any : InputType) => boolean;
-export type Type<T> = readonly [Converter<T>, Validator<false>?, boolean?];
+export type Type<T> = readonly [Converter<T>, Validator<false>?, (boolean | 'convert')?];
 
 export interface Types {
     // String outputs
@@ -95,7 +95,7 @@ export const Types: Types = {
     Float: [(v) => +v, (v) => Number.isFinite(+v)],
 
     ObjectID: [(v) => new ObjectID(v), ObjectID.isValid],
-    Boolean: [(v) => v && !['false', 'off'].includes(v), null, true],
+    Boolean: [(v) => !!(v && !['false', 'off'].includes(v)), null, 'convert'],
     Date: [
         (v) => {
             const d = v.split('-');
diff --git a/packages/hydrooj/src/service/decorators.ts b/packages/hydrooj/src/service/decorators.ts
index ba8fb62d..40151dc0 100644
--- a/packages/hydrooj/src/service/decorators.ts
+++ b/packages/hydrooj/src/service/decorators.ts
@@ -9,7 +9,7 @@ type ClassDecorator = <T extends new (...args: any[]) => any>(Class: T) => T ext
 export interface ParamOption<T> {
     name: string,
     source: 'all' | 'get' | 'post' | 'route',
-    isOptional?: boolean,
+    isOptional?: boolean | 'convert',
     convert?: Converter<T>,
     validate?: Validator,
 }
@@ -60,6 +60,8 @@ function _descriptor(v: ParamOption<any>) {
                         if (item.validate && !item.validate(value)) throw new ValidationError(item.name);
                         if (item.convert) c.push(item.convert(value));
                         else c.push(value);
+                    } else if (item.isOptional === 'convert') {
+                        c.push(item.convert ? item.convert(value) : value);
                     } else c.push(undefined);
                 }
                 return originalMethod.call(this, ...c);