diff --git a/packages/hydrooj/src/handler/contest.ts b/packages/hydrooj/src/handler/contest.ts
index 3d604cd97..34fcb96da 100644
--- a/packages/hydrooj/src/handler/contest.ts
+++ b/packages/hydrooj/src/handler/contest.ts
@@ -557,7 +557,7 @@ export class ContestManagementHandler extends ContestManagementBaseHandler {
     }
 
     @param('tid', Types.ObjectID)
-    @post('files', Types.Array)
+    @post('files', Types.ArrayOf(Types.Name))
     async postDeleteFiles(domainId: string, tid: ObjectID, files: string[]) {
         await Promise.all([
             storage.del(files.map((t) => `contest/${domainId}/${tid}/${t}`), this.user._id),
diff --git a/packages/hydrooj/src/handler/domain.ts b/packages/hydrooj/src/handler/domain.ts
index 1a67e0181..e4ad78cfc 100644
--- a/packages/hydrooj/src/handler/domain.ts
+++ b/packages/hydrooj/src/handler/domain.ts
@@ -224,7 +224,7 @@ class DomainRoleHandler extends ManageHandler {
     }
 
     @requireSudo
-    @param('roles', Types.Array)
+    @param('roles', Types.ArrayOf(Types.Name))
     async postDelete(domainId: string, roles: string[]) {
         if (Set.intersection(roles, ['root', 'default', 'guest']).size > 0) {
             throw new ValidationError('role', null, 'You cannot delete root, default or guest roles');
diff --git a/packages/hydrooj/src/handler/misc.ts b/packages/hydrooj/src/handler/misc.ts
index 4f98311d8..a703593c7 100644
--- a/packages/hydrooj/src/handler/misc.ts
+++ b/packages/hydrooj/src/handler/misc.ts
@@ -69,7 +69,7 @@ export class FilesHandler extends Handler {
         this.back();
     }
 
-    @post('files', Types.Array)
+    @post('files', Types.ArrayOf(Types.Name))
     async postDeleteFiles(domainId: string, files: string[]) {
         await Promise.all([
             storage.del(files.map((t) => `user/${this.user._id}/${t}`), this.user._id),
diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index a9aad08d8..9b3cd74e7 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -784,7 +784,7 @@ export class ProblemFilesHandler extends ProblemDetailHandler {
         this.back();
     }
 
-    @post('files', Types.Array)
+    @post('files', Types.ArrayOf(Types.Name))
     @post('type', Types.Range(['testdata', 'additional_file']), true)
     async postDeleteFiles(domainId: string, files: string[], type = 'testdata') {
         if (this.pdoc.reference) throw new ProblemIsReferencedError('delete files');
diff --git a/packages/hydrooj/src/handler/training.ts b/packages/hydrooj/src/handler/training.ts
index dc7c19e1a..0b5ee44d2 100644
--- a/packages/hydrooj/src/handler/training.ts
+++ b/packages/hydrooj/src/handler/training.ts
@@ -279,7 +279,7 @@ export class TrainingFilesHandler extends Handler {
     }
 
     @param('tid', Types.ObjectID)
-    @post('files', Types.Array)
+    @post('files', Types.ArrayOf(Types.Name))
     async postDeleteFiles(domainId: string, tid: ObjectID, files: string[]) {
         await Promise.all([
             storage.del(files.map((t) => `contest/${domainId}/${tid}/${t}`), this.user._id),
diff --git a/packages/hydrooj/src/service/decorators.ts b/packages/hydrooj/src/service/decorators.ts
index 8e07f2c9f..fc0570e6f 100644
--- a/packages/hydrooj/src/service/decorators.ts
+++ b/packages/hydrooj/src/service/decorators.ts
@@ -12,7 +12,7 @@ import type { Handler } from './server';
 type MethodDecorator = (target: any, name: string, obj: any) => any;
 type InputType = string | number | Record<string, any> | any[];
 type Converter<T> = (value: any) => T;
-type Validator = (value: InputType) => boolean;
+type Validator<Loose extends boolean = true> = (value: Loose extends true ? any : InputType) => boolean;
 export interface ParamOption<T> {
     name: string,
     source: 'all' | 'get' | 'post' | 'route',
@@ -21,7 +21,7 @@ export interface ParamOption<T> {
     validate?: Validator,
 }
 
-type Type<T> = [Converter<T>, Validator?, boolean?];
+type Type<T> = [Converter<T>, Validator<false>?, boolean?];
 
 export interface Types {
     Content: Type<string>;
@@ -117,6 +117,7 @@ export const Types: Types = {
             return false;
         },
     ],
+    /** @deprecated suggested to use Types.ArrayOf instead. */
     Array: [(v) => {
         if (v instanceof Array) return v;
         return v ? [v] : [];
diff --git a/packages/hydrooj/src/service/server.ts b/packages/hydrooj/src/service/server.ts
index 5514aa335..297379063 100644
--- a/packages/hydrooj/src/service/server.ts
+++ b/packages/hydrooj/src/service/server.ts
@@ -167,7 +167,7 @@ export class HandlerCommon {
 export class Handler extends HandlerCommon {
     loginMethods: any;
     noCheckPermView = false;
-    __param: Record<string, decorators.ParamOption[]>;
+    __param: Record<string, decorators.ParamOption<any>[]>;
 
     back(body?: any) {
         this.response.body = body || this.response.body || {};