diff --git a/src/components/i18n/actions.js b/src/components/i18n/actions.js
index 9869ffa..4224f1c 100644
--- a/src/components/i18n/actions.js
+++ b/src/components/i18n/actions.js
@@ -1,26 +1,26 @@
+// @flow
 import i18n from 'services/i18n';
 import captcha from 'services/captcha';
 
 export const SET_LOCALE = 'i18n:setLocale';
-export function setLocale(locale) {
-    return (dispatch) => i18n.require(
-        i18n.detectLanguage(locale)
-    ).then(({locale, messages}) => {
-        dispatch(_setLocale({locale, messages}));
+export function setLocale(desiredLocale: string) {
+    return async (dispatch: (action: Object) => any) => {
+        const { locale, messages } = await i18n.require(i18n.detectLanguage(desiredLocale));
+        dispatch(_setLocale(locale, messages));
 
         // TODO: probably should be moved from here, because it is a side effect
         captcha.setLang(locale);
 
         return locale;
-    });
+    };
 }
 
-function _setLocale({locale, messages}) {
+function _setLocale(locale: string, messages: { [string]: string }) {
     return {
         type: SET_LOCALE,
         payload: {
             locale,
-            messages
-        }
+            messages,
+        },
     };
 }
diff --git a/src/components/languageSwitcher/LanguageList.js b/src/components/languageSwitcher/LanguageList.js
index 91c7917..9122924 100644
--- a/src/components/languageSwitcher/LanguageList.js
+++ b/src/components/languageSwitcher/LanguageList.js
@@ -18,14 +18,14 @@ import type { LocalesMap } from './LanguageSwitcher';
 const itemHeight = 51;
 
 export default class LanguageList extends React.Component<{
-    userLang: string,
+    selectedLocale: string,
     langs: LocalesMap,
     onChangeLang: (lang: string) => void,
 }> {
     emptyListStateInner: ?HTMLDivElement;
 
     render() {
-        const { userLang, langs } = this.props;
+        const { selectedLocale, langs } = this.props;
         const isListEmpty = Object.keys(langs).length === 0;
         const firstLocale = Object.keys(langs)[0] || null;
         const emptyCaption = this.getEmptyCaption();
@@ -67,7 +67,7 @@ export default class LanguageList extends React.Component<{
                                 key={locale}
                                 style={style}
                                 className={classNames(styles.languageItem, {
-                                    [styles.activeLanguageItem]: locale === userLang,
+                                    [styles.activeLanguageItem]: locale === selectedLocale,
                                     [styles.firstLanguageItem]: locale === firstLocale,
                                 })}
                                 onClick={this.onChangeLang(locale)}
diff --git a/src/components/languageSwitcher/LanguageSwitcher.js b/src/components/languageSwitcher/LanguageSwitcher.js
index fbb59ad..ae401ba 100644
--- a/src/components/languageSwitcher/LanguageSwitcher.js
+++ b/src/components/languageSwitcher/LanguageSwitcher.js
@@ -11,7 +11,7 @@ import styles from './languageSwitcher.scss';
 import messages from './languageSwitcher.intl.json';
 import LanguageList from './LanguageList';
 
-const translateUrl = 'https://translate.ely.by/project/elyby/invite';
+const translateUrl = 'http://ely.by/translate';
 
 export type LocaleData = {
     code: string,
@@ -25,7 +25,7 @@ export type LocalesMap = {[code: string]: LocaleData};
 
 class LanguageSwitcher extends Component<{
     onClose: Function,
-    userLang: string,
+    selectedLocale: string,
     changeLang: (lang: string) => void,
     langs: LocalesMap,
     emptyCaptions: Array<{
@@ -51,7 +51,7 @@ class LanguageSwitcher extends Component<{
     };
 
     render() {
-        const { userLang, onClose } = this.props;
+        const { selectedLocale, onClose } = this.props;
         const { filteredLangs } = this.state;
 
         return (
@@ -80,7 +80,7 @@ class LanguageSwitcher extends Component<{
                         </div>
 
                         <LanguageList
-                            userLang={userLang}
+                            selectedLocale={selectedLocale}
                             langs={filteredLangs}
                             onChangeLang={this.onChangeLang}
                         />
@@ -157,7 +157,7 @@ import { connect } from 'react-redux';
 import { changeLang } from 'components/user/actions';
 
 export default connect((state) => ({
-    userLang: state.user.lang,
+    selectedLocale: state.i18n.locale,
 }), {
     changeLang,
 })(LanguageSwitcher);
diff --git a/src/components/languageSwitcher/changeLanguageLink/ChangeLanguageLink.js b/src/components/languageSwitcher/changeLanguageLink/ChangeLanguageLink.js
index 547792e..d978a3c 100644
--- a/src/components/languageSwitcher/changeLanguageLink/ChangeLanguageLink.js
+++ b/src/components/languageSwitcher/changeLanguageLink/ChangeLanguageLink.js
@@ -1,31 +1,43 @@
 // @flow
 import React from 'react';
-import { connect } from 'react-redux';
-import { create as createPopup } from 'components/ui/popup/actions';
+import classNames from 'classnames';
 import { localeFlags } from 'components/i18n';
 import LANGS from 'i18n/index.json';
-import LanguageSwitcher from '../LanguageSwitcher';
 import styles from './link.scss';
 
 function LanguageLink({
     userLang,
+    interfaceLocale,
     showLanguageSwitcherPopup,
 }: {
-    userLang: string,
-    showLanguageSwitcherPopup: Function,
+    userLang: string;
+    interfaceLocale: string;
+    showLanguageSwitcherPopup: Function;
 }) {
+    const localeDefinition = LANGS[userLang] || LANGS[interfaceLocale];
+
     return (
-        <span className={styles.languageLink} onClick={showLanguageSwitcherPopup}>
+        <span
+            className={classNames(styles.languageLink, {
+                [styles.mark]: userLang !== interfaceLocale,
+            })}
+            onClick={showLanguageSwitcherPopup}
+        >
             <span className={styles.languageIcon} style={{
-                backgroundImage: `url('${localeFlags.getIconUrl(userLang)}')`
+                backgroundImage: `url('${localeFlags.getIconUrl(localeDefinition.code)}')`,
             }} />
-            {LANGS[userLang].name}
+            {localeDefinition.name}
         </span>
     );
 }
 
+import { connect } from 'react-redux';
+import { create as createPopup } from 'components/ui/popup/actions';
+import LanguageSwitcher from 'components/languageSwitcher';
+
 export default connect((state) => ({
     userLang: state.user.lang,
+    interfaceLocale: state.i18n.locale,
 }), {
     showLanguageSwitcherPopup: () => createPopup(LanguageSwitcher),
 })(LanguageLink);
diff --git a/src/components/languageSwitcher/changeLanguageLink/link.scss b/src/components/languageSwitcher/changeLanguageLink/link.scss
index 61ef597..210a129 100644
--- a/src/components/languageSwitcher/changeLanguageLink/link.scss
+++ b/src/components/languageSwitcher/changeLanguageLink/link.scss
@@ -1,9 +1,23 @@
+@import '~components/ui/colors.scss';
+
 .languageLink {
+    position: relative;
+
     color: #666;
     border-bottom: 1px dotted #666;
     text-decoration: none;
     transition: .25s;
     cursor: pointer;
+
+    &.mark {
+        &:after {
+            position: absolute;
+            content: '*';
+            color: $red;
+            font-size: 75%;
+            top: -0.20em;
+        }
+    }
 }
 
 .languageIcon {
diff --git a/src/components/profile/Profile.intl.json b/src/components/profile/Profile.intl.json
index 69a52be..06f0c67 100644
--- a/src/components/profile/Profile.intl.json
+++ b/src/components/profile/Profile.intl.json
@@ -12,6 +12,8 @@
     "email": "E‑mail:",
     "password": "Password:",
     "siteLanguage": "Site language:",
+    "languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
+    "participateInTheTranslation": "participate in the translation",
     "twoFactorAuth": "Two‑factor auth:",
     "uuid": "UUID:"
 }
diff --git a/src/components/profile/Profile.js b/src/components/profile/Profile.js
index 041d530..f1696c3 100644
--- a/src/components/profile/Profile.js
+++ b/src/components/profile/Profile.js
@@ -14,12 +14,13 @@ import RulesPage from 'pages/rules/RulesPage';
 import type { User } from 'components/user';
 
 class Profile extends Component<{
-    user: User
+    user: User;
+    interfaceLocale: string;
 }> {
     UUID: ?HTMLElement;
 
     render() {
-        const { user } = this.props;
+        const { user, interfaceLocale } = this.props;
 
         return (
             <div>
@@ -85,6 +86,16 @@ class Profile extends Component<{
                             <ProfileField
                                 label={<Message {...messages.siteLanguage} />}
                                 value={<ChangeLanguageLink />}
+                                warningMessage={user.lang === interfaceLocale ? '' : (
+                                    <Message {...messages.languageIsUnavailableWarning} values={{
+                                        locale: user.lang,
+                                        participateInTheTranslation: (
+                                            <a href="http://ely.by/translate" target="_blank">
+                                                <Message {...messages.participateInTheTranslation} />
+                                            </a>
+                                        ),
+                                    }}/>
+                                )}
                             />
 
                             <ProfileField
@@ -139,8 +150,10 @@ class Profile extends Component<{
     }
 }
 
-export default connect(({ user }): {
-    user: User,
+export default connect(({ user, i18n }): {
+    user: User;
+    interfaceLocale: string;
 } => ({
     user,
+    interfaceLocale: i18n.locale,
 }))(Profile);
diff --git a/src/i18n/be.json b/src/i18n/be.json
index 91dd369..4834fa2 100644
--- a/src/i18n/be.json
+++ b/src/i18n/be.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Не ўключана",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Уключана",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Знойдзены акаўнт Mojang з такім жа нікам і, па {rules}, яго ўладальнік мае права патрабаваць аднаўленне кантролю над нікам.",
     "components.profile.multiFactorAuth.codePlaceholder": "Увядзіце код сюды",
     "components.profile.multiFactorAuth.disable": "Адключыць",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Дадатак устаноўлены",
     "components.profile.multiFactorAuth.whenKeyEntered": "Убачыўшы ў дадатку часовы код, перайдзіце да наступнага кроку.",
     "components.profile.nickname": "Нік:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Пароль:",
     "components.profile.passwordRequestForm.continue": "Працягнуць",
     "components.profile.passwordRequestForm.description": "Каб завершыць, увядзіце пароль ад акаўнта",
diff --git a/src/i18n/en.json b/src/i18n/en.json
index a3c5279..307c981 100644
--- a/src/i18n/en.json
+++ b/src/i18n/en.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Disabled",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Enabled",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "A Mojang account with the same nickname was found. According to {rules}, account owner has the right to demand the restoration of control over nickname.",
     "components.profile.multiFactorAuth.codePlaceholder": "Enter the code here",
     "components.profile.multiFactorAuth.disable": "Disable",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "App has been installed",
     "components.profile.multiFactorAuth.whenKeyEntered": "If a temporary code appears in your two‑factor auth app, then you may proceed to the next step.",
     "components.profile.nickname": "Nickname:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Password:",
     "components.profile.passwordRequestForm.continue": "Continue",
     "components.profile.passwordRequestForm.description": "To complete action enter the account password",
diff --git a/src/i18n/fr.json b/src/i18n/fr.json
index bf3c215..08b0799 100644
--- a/src/i18n/fr.json
+++ b/src/i18n/fr.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Désactivée",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Activer",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Un compte Mojang avec le même pseudo a été trouvé. Selon les {rules}, le propriétaire du compte a le droit d'exiger la restauration du contrôle sur le surnom.",
     "components.profile.multiFactorAuth.codePlaceholder": "Entrez le code ici",
     "components.profile.multiFactorAuth.disable": "Désactiver",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "L'application a été installé",
     "components.profile.multiFactorAuth.whenKeyEntered": "If a temporary code appears in your two‑factor auth app, then you may proceed to the next step.",
     "components.profile.nickname": "Surnom:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Mot de passe:",
     "components.profile.passwordRequestForm.continue": "Continuer",
     "components.profile.passwordRequestForm.description": "Pour compléter cette action, entrez le mot de passe du compte",
diff --git a/src/i18n/id.json b/src/i18n/id.json
index c45c098..e2ecb02 100644
--- a/src/i18n/id.json
+++ b/src/i18n/id.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Dinonaktifkan",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Diaktifkan",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Mojang akun dengan nickname yang sama di temukan. Sesuai dengan {rules}, pemilik akun dapat mengambil kontrol dengan nickname-nya.",
     "components.profile.multiFactorAuth.codePlaceholder": "Masukkan kodenya disini",
     "components.profile.multiFactorAuth.disable": "Nonaktifkan",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Aplikasi telah diunduh",
     "components.profile.multiFactorAuth.whenKeyEntered": "Jika kode sementara muncul di aplikasi otorisasi dua-faktor anda, anda boleh lanjut ke tahap berikutnya.",
     "components.profile.nickname": "Nama panggilan:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Kata sandi:",
     "components.profile.passwordRequestForm.continue": "Lanjut",
     "components.profile.passwordRequestForm.description": "Untuk menyelesaikan, masukan kata sandi",
diff --git a/src/i18n/lt.json b/src/i18n/lt.json
index 1d64403..a655ba8 100644
--- a/src/i18n/lt.json
+++ b/src/i18n/lt.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Išjungtas",
     "components.profile.email": "El.Paštas:",
     "components.profile.enabled": "Įjungtas",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Buvo rasta Mojang paskyra su tuo pačiu slapyvardžiu. Pagal {rules}, paskyros savininkas turi teisę reikalauti atkurti slapyvardžio kontrolę.",
     "components.profile.multiFactorAuth.codePlaceholder": "Įveskite kodą čia",
     "components.profile.multiFactorAuth.disable": "Išjungti",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Programa įdiegta",
     "components.profile.multiFactorAuth.whenKeyEntered": "Jei dviejų veiksmų programoje pasirodo laikinas kodas, galite pereiti prie kito žingsnio.",
     "components.profile.nickname": "Slapyvardis:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Slaptažodis:",
     "components.profile.passwordRequestForm.continue": "Tęsti",
     "components.profile.passwordRequestForm.description": "Norėdami užbaigti veiksmą įveskite paskyros slaptažodį",
diff --git a/src/i18n/pl.json b/src/i18n/pl.json
index e9efd93..31263ab 100644
--- a/src/i18n/pl.json
+++ b/src/i18n/pl.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Wyłączone",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Włączone",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Znaleziono konto Mojang z tym samym nickiem. Zgodnie z {rules} właściciel konta ma prawo żądać przywrócenia kontroli nad pseudonimem.",
     "components.profile.multiFactorAuth.codePlaceholder": "Wprowadź tutaj kod",
     "components.profile.multiFactorAuth.disable": "Wyłącz",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Aplikacja została zainstalowana",
     "components.profile.multiFactorAuth.whenKeyEntered": "Jeżeli kod tymczasowy pojawia się w twojej aplikacji uwierzytelniania dwupoziomowego, możesz przejść do następnego kroku.",
     "components.profile.nickname": "Nick:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Hasło:",
     "components.profile.passwordRequestForm.continue": "Kontynuuj",
     "components.profile.passwordRequestForm.description": "Aby zakończyć działanie, wprowadź hasło konta",
diff --git a/src/i18n/pt.json b/src/i18n/pt.json
index ba20609..ea73279 100644
--- a/src/i18n/pt.json
+++ b/src/i18n/pt.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Desativado",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Habilitado",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Uma conta da Mojang com o mesmo nome foi encontrada. De acordo com as {rules}, o dono desta conta tem o poder de controlar este apelido.",
     "components.profile.multiFactorAuth.codePlaceholder": "Digite o código aqui",
     "components.profile.multiFactorAuth.disable": "Desabilitar",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Aplicativo instalado",
     "components.profile.multiFactorAuth.whenKeyEntered": "Se um código temporário aparece no seu app de aut. em dois fatores, então você pode prosseguir para a próxima etapa.",
     "components.profile.nickname": "Apelido:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Senha:",
     "components.profile.passwordRequestForm.continue": "Continuar",
     "components.profile.passwordRequestForm.description": "Para completar a ação, coloque a senha da conta",
diff --git a/src/i18n/ru.json b/src/i18n/ru.json
index 83897b9..7fe70a1 100644
--- a/src/i18n/ru.json
+++ b/src/i18n/ru.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Не включена",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Включена",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Найден аккаунт Mojang с таким же ником. Учтите, что согласно с {rules}, его владелец вправе потребовать восстановления контроля над ником.",
     "components.profile.multiFactorAuth.codePlaceholder": "Введите сюда код",
     "components.profile.multiFactorAuth.disable": "Отключить",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Приложение установлено",
     "components.profile.multiFactorAuth.whenKeyEntered": "После того, как вы увидели в приложении временный код, переходите к следующему шагу.",
     "components.profile.nickname": "Ник:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Пароль:",
     "components.profile.passwordRequestForm.continue": "Продолжить",
     "components.profile.passwordRequestForm.description": "Для завершения, укажите пароль от аккаунта",
diff --git a/src/i18n/sr.json b/src/i18n/sr.json
index 04a2033..8953e21 100644
--- a/src/i18n/sr.json
+++ b/src/i18n/sr.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "онемогућена",
     "components.profile.email": "Е-пошта:",
     "components.profile.enabled": "омогућена",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Пронађен је Mojang налог са истим надимком. Према {rules}, власник налога има право да затражи враћање контроле над надимком.",
     "components.profile.multiFactorAuth.codePlaceholder": "Овде унесите кôд",
     "components.profile.multiFactorAuth.disable": "Онемогући",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Апликација је инсталирана",
     "components.profile.multiFactorAuth.whenKeyEntered": "Ако се привремени кôд појави у апликацији за потврду идентитета помоћу два фактора, можете прећи на следећи корак.",
     "components.profile.nickname": "Надимак:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Лозинка:",
     "components.profile.passwordRequestForm.continue": "Настави",
     "components.profile.passwordRequestForm.description": "Да бисте довршили радњу, унесите лозинку налога",
diff --git a/src/i18n/uk.json b/src/i18n/uk.json
index ae89164..f8b67e0 100644
--- a/src/i18n/uk.json
+++ b/src/i18n/uk.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Вимкнено",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Увімкнена",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Знайдений акаунт Mojang з таким же ніком. Майте на увазі, що згідно з {rules}, його власник має право вимагати відновлення контролю над ніком.",
     "components.profile.multiFactorAuth.codePlaceholder": "Вкажіть код сюди",
     "components.profile.multiFactorAuth.disable": "Вимкнути",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Додаток встановлено",
     "components.profile.multiFactorAuth.whenKeyEntered": "Після того, як ви побачили в додатку тимчасовий код, перейдіть до наступного кроку.",
     "components.profile.nickname": "Нік:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Пароль:",
     "components.profile.passwordRequestForm.continue": "Продовжити",
     "components.profile.passwordRequestForm.description": "Для завершення, вкажіть пароль від акаунту",
diff --git a/src/i18n/vi.json b/src/i18n/vi.json
index 705a6d2..baebf0a 100644
--- a/src/i18n/vi.json
+++ b/src/i18n/vi.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "Đã vô hiệu hóa",
     "components.profile.email": "E‑mail:",
     "components.profile.enabled": "Đã kích hoạt",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "Một tài khoản Mojang với nickname này đã được tìm thấy. Theo {rules}, chủ của tài khoản có quyền được lấy lại nickname của mình.",
     "components.profile.multiFactorAuth.codePlaceholder": "Nhập mã vào đây",
     "components.profile.multiFactorAuth.disable": "Vô hiệu hoá",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "Ứng dụng đã được cài đặt",
     "components.profile.multiFactorAuth.whenKeyEntered": "Nếu xuất hiện một mã tạm thời trong ứng dụng xác thực 2 bước thì bạn đã sẵn sàng để đến với bước kế tiếp.",
     "components.profile.nickname": "Nickname:",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "Mật khẩu:",
     "components.profile.passwordRequestForm.continue": "Tiếp tục",
     "components.profile.passwordRequestForm.description": "Để hoàn tất hành động hãy nhập mật khẩu tài khoản",
diff --git a/src/i18n/zh.json b/src/i18n/zh.json
index 0e16d20..75112bd 100644
--- a/src/i18n/zh.json
+++ b/src/i18n/zh.json
@@ -177,6 +177,7 @@
     "components.profile.disabled": "禁用 ",
     "components.profile.email": "Email：",
     "components.profile.enabled": "启用",
+    "components.profile.languageIsUnavailableWarning": "The locale \"{locale}\" you've used earlier isn't currently translated enough. If you want to continue using the selected language, please {participateInTheTranslation} of the project.",
     "components.profile.mojangPriorityWarning": "找到一个具有相同昵称的Mojang帐户。根据{rules}，账户拥有者有权要求恢复对昵称的控制权。",
     "components.profile.multiFactorAuth.codePlaceholder": "在这里输入代码",
     "components.profile.multiFactorAuth.disable": "禁用",
@@ -198,6 +199,7 @@
     "components.profile.multiFactorAuth.theAppIsInstalled": "应用程序已成功安装",
     "components.profile.multiFactorAuth.whenKeyEntered": "如果临时代码出现在双重认证应用程序中，则可以继续下一步。",
     "components.profile.nickname": "名称：",
+    "components.profile.participateInTheTranslation": "participate in the translation",
     "components.profile.password": "密码：",
     "components.profile.passwordRequestForm.continue": "继续",
     "components.profile.passwordRequestForm.description": "要完成操作，请输入原帐户密码",
diff --git a/src/services/i18n.js b/src/services/i18n.js
index f015582..cf72d77 100644
--- a/src/services/i18n.js
+++ b/src/services/i18n.js
@@ -1,3 +1,4 @@
+// @flow
 import locales from 'i18n/index.json';
 
 import { addLocaleData } from 'react-intl';
@@ -7,37 +8,40 @@ const DEFAULT_LANGUAGE = 'en';
 
 const needPolyfill = !window.Intl;
 
-function getUserLanguages(userSelectedLang = []) {
-    return [].concat(userSelectedLang || [])
+function getUserLanguages(userSelectedLang: string): Array<string> {
+    return [userSelectedLang]
         .concat(navigator.languages || [])
         .concat(navigator.language || []);
 }
 
-function detectLanguage(userLanguages, availableLanguages, defaultLanguage) {
-    return (userLanguages || [])
-        .concat(defaultLanguage)
+function detectLanguage(
+    userLanguages: Array<string>,
+    availableLanguages: Array<string>,
+    defaultLanguage: string,
+): string {
+    return userLanguages
         .map((lang) => lang.split('-').shift().toLowerCase())
-        .find((lang) => availableLanguages.indexOf(lang) !== -1);
+        .find((lang) => availableLanguages.indexOf(lang) !== -1) || defaultLanguage;
 }
 
 export default {
-    detectLanguage(lang) {
+    detectLanguage(lang: string): string {
         return detectLanguage(getUserLanguages(lang), SUPPORTED_LANGUAGES, DEFAULT_LANGUAGE);
     },
 
-    require(locale) {
-        const promises = [
+    require(locale: string): Promise<{
+        locale: string;
+        messages: { [string]: string };
+    }> {
+        const promises: Array<Promise<*>> = [
             new Promise(require(`bundle?name=[name]!react-intl/locale-data/${locale}.js`)),
             new Promise(require(`bundle?name=[name]!i18n/${locale}.json`))
         ];
 
         if (needPolyfill) {
-            promises.push(
-                new Promise(require('bundle?name=intl!intl')),
-            );
-            promises.push(
-                new Promise(require(`bundle?name=[name]-polyfill-data!intl/locale-data/jsonp/${locale}.js`)),
-            );
+            // $FlowFixMe
+            promises.push(new Promise(require('bundle?name=intl!intl')));
+            promises.push(new Promise(require(`bundle?name=[name]-polyfill-data!intl/locale-data/jsonp/${locale}.js`)));
         }
 
         return Promise.all(promises)