diff --git a/app/lib/server/functions/checkUsernameAvailability.js b/app/lib/server/functions/checkUsernameAvailability.js
index 765bd37158a39..f152e93266b79 100644
--- a/app/lib/server/functions/checkUsernameAvailability.js
+++ b/app/lib/server/functions/checkUsernameAvailability.js
@@ -1,5 +1,6 @@
 import { Meteor } from 'meteor/meteor';
 import s from 'underscore.string';
+import _ from 'underscore';
 import { escapeRegExp } from '@rocket.chat/string-helpers';
 
 import { settings } from '../../../settings';
@@ -19,7 +20,7 @@ const usernameIsBlocked = (username, usernameBlackList) => usernameBlackList.len
 
 export const checkUsernameAvailability = function(username) {
 	if (usernameIsBlocked(username, usernameBlackList) || !validateName(username)) {
-		return false;
+		throw new Meteor.Error('error-blocked-username', `${ _.escape(username) } is blocked and can't be used!`, { method: 'checkUsernameAvailability', field: username });
 	}
 
 	// Make sure no users are using this username
diff --git a/app/ui-login/client/username/username.html b/app/ui-login/client/username/username.html
index 506a530d47490..9ede3ba2fdb27 100644
--- a/app/ui-login/client/username/username.html
+++ b/app/ui-login/client/username/username.html
@@ -6,7 +6,12 @@
 					<h2>{{_ "Username_title"}}</h2>
 					<p>{{_ "Username_description"}}</p>
 				</header>
-				{{#if username.error}}
+				{{#if username.blocked}}
+					<div class="alert error-color error-background error-border">
+						{{{_ "error-blocked-username" field=username.escaped}}}
+					</div>
+				{{/if}}
+				{{#if username.unavailable}}
 					<div class="alert error-color error-background error-border">
 						{{{_ "error-field-unavailable" field=username.escaped}}}
 					</div>
diff --git a/app/ui-login/client/username/username.js b/app/ui-login/client/username/username.js
index 12bafe6517a01..125f34ddc7fc6 100644
--- a/app/ui-login/client/username/username.js
+++ b/app/ui-login/client/username/username.js
@@ -69,11 +69,12 @@ Template.username.events({
 
 		return Meteor.call('setUsername', value, function(err) {
 			if (err != null) {
-				console.log(err);
 				if (err.error === 'username-invalid') {
 					username.invalid = true;
+				} else if (err.error === 'error-blocked-username') {
+					username.blocked = true;
 				} else {
-					username.error = true;
+					username.unavailable = true;
 				}
 				username.username = value;
 				username.escaped = _.escape(value);
diff --git a/packages/rocketchat-i18n/i18n/en.i18n.json b/packages/rocketchat-i18n/i18n/en.i18n.json
index 64475d5ecb0fd..8586156f52f3e 100644
--- a/packages/rocketchat-i18n/i18n/en.i18n.json
+++ b/packages/rocketchat-i18n/i18n/en.i18n.json
@@ -1615,6 +1615,7 @@
   "error-avatar-invalid-url": "Invalid avatar URL: __url__",
   "error-avatar-url-handling": "Error while handling avatar setting from a URL (__url__) for __username__",
   "error-business-hours-are-closed": "Business Hours are closed",
+  "error-blocked-username": "<strong>__field__</strong> is blocked and can't be used!",
   "error-canned-response-not-found": "Canned Response Not Found",
   "error-cannot-delete-app-user": "Deleting app user is not allowed, uninstall the corresponding app to remove it.",
   "error-cant-invite-for-direct-room": "Can't invite user to direct rooms",
diff --git a/packages/rocketchat-i18n/i18n/pt-BR.i18n.json b/packages/rocketchat-i18n/i18n/pt-BR.i18n.json
index 31675589af636..9132b3c64c575 100644
--- a/packages/rocketchat-i18n/i18n/pt-BR.i18n.json
+++ b/packages/rocketchat-i18n/i18n/pt-BR.i18n.json
@@ -1373,6 +1373,7 @@
   "error-archived-duplicate-name": "Já há um canal arquivado com o nome '__room_name__'",
   "error-avatar-invalid-url": "URL inválida de avatar: __url__",
   "error-avatar-url-handling": "Erro durante o manuseio configuração avatar a partir de uma URL (__url__) para __username__",
+  "error-blocked-username": "<strong>__field__</strong> está bloqueado e não pode ser usado!",
   "error-business-hours-are-closed": "Horário de expediente fechado",
   "error-cant-invite-for-direct-room": "Não é possível convidar usuários para salas diretas",
   "error-channels-setdefault-is-same": "A configuração padrão do canal é a mesma que seria alterada.",
diff --git a/tests/end-to-end/api/01-users.js b/tests/end-to-end/api/01-users.js
index 1a497af06a1c5..66137c0d8c66e 100644
--- a/tests/end-to-end/api/01-users.js
+++ b/tests/end-to-end/api/01-users.js
@@ -175,7 +175,7 @@ describe('[Users]', function() {
 					.expect(400)
 					.expect((res) => {
 						expect(res.body).to.have.property('success', false);
-						expect(res.body).to.have.property('error', `${ name } is already in use :( [error-field-unavailable]`);
+						expect(res.body).to.have.property('error', `${ name } is blocked and can't be used! [error-blocked-username]`);
 					})
 					.end(done);
 			});