diff --git a/packages/integration-tests/src/logto-context.ts b/packages/integration-tests/src/logto-context.ts
index cd19e8feb..4016d8f31 100644
--- a/packages/integration-tests/src/logto-context.ts
+++ b/packages/integration-tests/src/logto-context.ts
@@ -53,8 +53,8 @@ export class LogtoContext {
 
   public async init() {
     const account = {
-      username: generatePassword(),
-      password: generateUsername(),
+      username: generateUsername(),
+      password: generatePassword(),
     };
     const codeVerifier = generateCodeVerifier();
     const codeChallenge = await generateCodeChallenge(codeVerifier);
diff --git a/packages/integration-tests/src/utils.ts b/packages/integration-tests/src/utils.ts
index 1d074b0b2..b775a513b 100644
--- a/packages/integration-tests/src/utils.ts
+++ b/packages/integration-tests/src/utils.ts
@@ -6,5 +6,5 @@ export const extractCookie = (response: Response) => {
   return headers['set-cookie']?.join('; ') ?? '';
 };
 
-export const generateUsername = () => `usr-${crypto.randomUUID()}`;
-export const generatePassword = () => `pwd-${crypto.randomUUID()}`;
+export const generateUsername = () => `usr_${crypto.randomUUID().replaceAll('-', '_')}`;
+export const generatePassword = () => `pwd_${crypto.randomUUID()}`;
diff --git a/packages/phrases-ui/src/locales/en.ts b/packages/phrases-ui/src/locales/en.ts
index 65cdfe745..9161572d9 100644
--- a/packages/phrases-ui/src/locales/en.ts
+++ b/packages/phrases-ui/src/locales/en.ts
@@ -58,7 +58,7 @@ const translation = {
     password_required: 'Password is required',
     username_exists: 'Username already exists',
     username_should_not_start_with_number: 'Username should not start with a number',
-    username_valid_charset: 'Username should only contain letters, numbers, or underscore.',
+    username_valid_charset: 'Username should only contain letters, numbers, or underscores.',
     invalid_email: 'The email is invalid',
     invalid_phone: 'The phone number is invalid',
     password_min_length: 'Password requires a minimum of {{min}} characters',
diff --git a/packages/shared/src/regex.ts b/packages/shared/src/regex.ts
index 603af7e5b..e28cb1931 100644
--- a/packages/shared/src/regex.ts
+++ b/packages/shared/src/regex.ts
@@ -1,6 +1,6 @@
 export const emailRegEx = /^\S+@\S+\.\S+$/;
 export const phoneRegEx = /^\d+$/;
-export const usernameRegEx = /^[A-Z_a-z-][\w-]*$/;
+export const usernameRegEx = /^[A-Z_a-z]\w*$/;
 export const passwordRegEx = /^.{6,}$/;
 export const redirectUriRegEx = /^https?:\/\//;
 export const hexColorRegEx = /^#[\da-f]{3}([\da-f]{3})?$/i;