3 files changed, 15 insertions, 3 deletions

diff --git a/server/helpers/custom-validators/users.ts b/server/helpers/custom-validators/users.ts
index f423d6317..b5b5642d6 100644
--- a/server/helpers/custom-validators/users.ts
+++ b/server/helpers/custom-validators/users.ts
@@ -18,7 +18,7 @@ function isUserVideoQuotaValid (value: string) {
 function isUserUsernameValid (value: string) {
   const max = USERS_CONSTRAINTS_FIELDS.USERNAME.max
   const min = USERS_CONSTRAINTS_FIELDS.USERNAME.min
-  return exists(value) && validator.matches(value, new RegExp(`^[a-zA-Z0-9._]{${min},${max}}$`))
+  return exists(value) && validator.matches(value, new RegExp(`^[a-z0-9._]{${min},${max}}$`))
 }
 
 function isUserDisplayNSFWValid (value: any) {
diff --git a/server/middlewares/validators/users.ts b/server/middlewares/validators/users.ts
index 0b463acc0..6b845f62b 100644
--- a/server/middlewares/validators/users.ts
+++ b/server/middlewares/validators/users.ts
@@ -19,7 +19,7 @@ import {
 import { UserInstance, VideoInstance } from '../../models'
 
 const usersAddValidator = [
-  body('username').custom(isUserUsernameValid).withMessage('Should have a valid username'),
+  body('username').custom(isUserUsernameValid).withMessage('Should have a valid username (lowercase alphanumeric characters)'),
   body('password').custom(isUserPasswordValid).withMessage('Should have a valid password'),
   body('email').isEmail().withMessage('Should have a valid email'),
   body('videoQuota').custom(isUserVideoQuotaValid).withMessage('Should have a valid user quota'),
@@ -196,7 +196,7 @@ function checkUserDoesNotAlreadyExist (username: string, email: string, res: exp
       .then(user => {
         if (user) {
           return res.status(409)
-                    .send({ error: 'User already exists.' })
+                    .send({ error: 'User with this username of email already exists.' })
                     .end()
         }
 
diff --git a/server/tests/api/check-params/users.ts b/server/tests/api/check-params/users.ts
index 687999c09..578fece49 100644
--- a/server/tests/api/check-params/users.ts
+++ b/server/tests/api/check-params/users.ts
@@ -112,6 +112,18 @@ describe('Test users API validators', function () {
       await makePostBodyRequest({ url: server.url, path, token: server.accessToken, fields })
     })
 
+    it('Should fail with a not lowercase username', async function () {
+      const fields = {
+        username: 'Toto',
+        email: 'test@example.com',
+        password: 'my_super_password',
+        videoQuota: 42000000,
+        role: UserRole.USER
+      }
+
+      await makePostBodyRequest({ url: server.url, path, token: server.accessToken, fields })
+    })
+
     it('Should fail with an incorrect username', async function () {
       const fields = {
         username: 'my username',