diff --git a/packages/core/src/queries/user.ts b/packages/core/src/queries/user.ts
index d2fc7526e..cc33cccfe 100644
--- a/packages/core/src/queries/user.ts
+++ b/packages/core/src/queries/user.ts
@@ -5,6 +5,13 @@ import { convertToIdentifiers, insertInto } from '@/database/utils';
 
 const { table, fields } = convertToIdentifiers(Users);
 
+export const findUserByUsername = async (username: string) =>
+  pool.one<UserDBEntry>(sql`
+  select ${sql.join(Object.values(fields), sql`,`)}
+  from ${table}
+  where ${fields.username}=${username}
+`);
+
 export const findUserById = async (id: string) =>
   pool.one<UserDBEntry>(sql`
   select ${sql.join(Object.values(fields), sql`,`)}
diff --git a/packages/core/src/routes/sign-in.ts b/packages/core/src/routes/sign-in.ts
index bf63df523..c7196a72e 100644
--- a/packages/core/src/routes/sign-in.ts
+++ b/packages/core/src/routes/sign-in.ts
@@ -2,7 +2,7 @@ import assert from 'assert';
 import Router from 'koa-router';
 import { object, string } from 'zod';
 import { encryptPassword } from '@/utils/password';
-import { findUserById } from '@/queries/user';
+import { findUserByUsername } from '@/queries/user';
 import { Provider } from 'oidc-provider';
 import { conditional } from '@logto/essentials';
 import koaGuard from '@/middleware/koa-guard';
@@ -13,20 +13,20 @@ export default function signInRoutes(provider: Provider) {
 
   router.post(
     '/sign-in',
-    koaGuard({ body: object({ id: string().optional(), password: string().optional() }) }),
+    koaGuard({ body: object({ username: string().optional(), password: string().optional() }) }),
     async (ctx) => {
       const {
         prompt: { name },
       } = await provider.interactionDetails(ctx.req, ctx.res);
 
       if (name === 'login') {
-        const { id, password } = ctx.guard.body;
+        const { username, password } = ctx.guard.body;
 
-        assert(id && password, new RequestError(SignInErrorCode.InsufficientInfo));
+        assert(username && password, new RequestError(SignInErrorCode.InsufficientInfo));
 
         try {
-          const { passwordEncrypted, passwordEncryptionMethod, passwordEncryptionSalt } =
-            await findUserById(id);
+          const { id, passwordEncrypted, passwordEncryptionMethod, passwordEncryptionSalt } =
+            await findUserByUsername(username);
 
           assert(
             passwordEncrypted && passwordEncryptionMethod && passwordEncryptionSalt,
diff --git a/packages/ui/src/apis/sign-in.ts b/packages/ui/src/apis/sign-in.ts
index 97120ca44..777858094 100644
--- a/packages/ui/src/apis/sign-in.ts
+++ b/packages/ui/src/apis/sign-in.ts
@@ -7,7 +7,7 @@ export const signInBasic = async (username: string, password: string) => {
   return ky
     .post('/api/sign-in', {
       json: {
-        id: username,
+        username,
         password,
       },
     })