diff --git a/docs/src/pages/docs/environments/error-files.mdx b/docs/src/pages/docs/environments/error-files.mdx
index 90da28c7c..d3f7566af 100644
--- a/docs/src/pages/docs/environments/error-files.mdx
+++ b/docs/src/pages/docs/environments/error-files.mdx
@@ -80,11 +80,12 @@ export default function RootLayout({children}) {
 For the 404 page to render, we need to call the `notFound` function in the root layout when we detect an incoming `locale` param that isn't a valid locale.
 
 ```tsx filename="app/[locale]/layout.tsx"
+import {isValidLocale} from 'next-intl';
 import {notFound} from 'next/navigation';
+import {routing} from '@/i18n/routing';
 
 export default function LocaleLayout({children, params: {locale}}) {
-  // Ensure that the incoming `locale` is valid
-  if (!routing.locales.includes(locale as any)) {
+  if (!isValidLocale(routing.locales, locale)) {
     notFound();
   }
 
diff --git a/docs/src/pages/docs/getting-started/app-router/with-i18n-routing.mdx b/docs/src/pages/docs/getting-started/app-router/with-i18n-routing.mdx
index e0d6ae9d1..f2f985ffa 100644
--- a/docs/src/pages/docs/getting-started/app-router/with-i18n-routing.mdx
+++ b/docs/src/pages/docs/getting-started/app-router/with-i18n-routing.mdx
@@ -295,12 +295,12 @@ export function generateStaticParams() {
 
 ```tsx filename="app/[locale]/layout.tsx"
 import {setRequestLocale} from 'next-intl/server';
+import {isValidLocale} from 'next-intl';
 import {notFound} from 'next/navigation';
 import {routing} from '@/i18n/routing';
 
 export default async function LocaleLayout({children, params: {locale}}) {
-  // Ensure that the incoming `locale` is valid
-  if (!routing.locales.includes(locale as any)) {
+  if (!isValidLocale(routing.locales, locale)) {
     notFound();
   }
 
diff --git a/examples/example-app-router-migration/src/app/[locale]/layout.tsx b/examples/example-app-router-migration/src/app/[locale]/layout.tsx
index 6864db0de..4e1c9cc72 100644
--- a/examples/example-app-router-migration/src/app/[locale]/layout.tsx
+++ b/examples/example-app-router-migration/src/app/[locale]/layout.tsx
@@ -1,5 +1,5 @@
 import {notFound} from 'next/navigation';
-import {NextIntlClientProvider} from 'next-intl';
+import {NextIntlClientProvider, isValidLocale} from 'next-intl';
 import {getMessages} from 'next-intl/server';
 import {ReactNode} from 'react';
 import {routing} from '@/i18n/routing';
@@ -10,8 +10,7 @@ type Props = {
 };
 
 export default async function LocaleLayout({children, params}: Props) {
-  // Ensure that the incoming `locale` is valid
-  if (!routing.locales.includes(params.locale as any)) {
+  if (!isValidLocale(routing.locales, params.locale)) {
     notFound();
   }
 
diff --git a/examples/example-app-router-migration/src/i18n/request.ts b/examples/example-app-router-migration/src/i18n/request.ts
index 70066e964..0534cbacd 100644
--- a/examples/example-app-router-migration/src/i18n/request.ts
+++ b/examples/example-app-router-migration/src/i18n/request.ts
@@ -1,14 +1,13 @@
+import {isValidLocale} from 'next-intl';
 import {getRequestConfig} from 'next-intl/server';
 import {routing} from './routing';
 
 export default getRequestConfig(async ({requestLocale}) => {
-  // This typically corresponds to the `[locale]` segment
-  let locale = await requestLocale;
-
-  // Ensure that the incoming locale is valid
-  if (!locale || !routing.locales.includes(locale as any)) {
-    locale = routing.defaultLocale;
-  }
+  // Typically corresponds to the `[locale]` segment
+  const requested = await requestLocale;
+  const locale = isValidLocale(routing.locales, requested)
+    ? requested
+    : routing.defaultLocale;
 
   return {
     locale,
diff --git a/examples/example-app-router-mixed-routing/global.d.ts b/examples/example-app-router-mixed-routing/global.d.ts
index b749518b9..dd933f191 100644
--- a/examples/example-app-router-mixed-routing/global.d.ts
+++ b/examples/example-app-router-mixed-routing/global.d.ts
@@ -1,8 +1,10 @@
+import 'next-intl';
+import {locales} from '@/config';
 import en from './messages/en.json';
 
-type Messages = typeof en;
-
-declare global {
-  // Use type safe message keys with `next-intl`
-  interface IntlMessages extends Messages {}
+declare module 'next-intl' {
+  interface AppConfig {
+    Locale: (typeof locales)[number];
+    Messages: typeof en;
+  }
 }
diff --git a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/PublicNavigationLocaleSwitcher.tsx b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/PublicNavigationLocaleSwitcher.tsx
index 45ce1900d..986e6e93d 100644
--- a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/PublicNavigationLocaleSwitcher.tsx
+++ b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/PublicNavigationLocaleSwitcher.tsx
@@ -1,7 +1,6 @@
 'use client';
 
-import {useLocale} from 'next-intl';
-import {Locale} from '@/config';
+import {Locale, useLocale} from 'next-intl';
 import {Link, usePathname} from '@/i18n/routing.public';
 
 export default function PublicNavigationLocaleSwitcher() {
diff --git a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/about/page.tsx b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/about/page.tsx
index 260a990c6..ffe4b971b 100644
--- a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/about/page.tsx
+++ b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/about/page.tsx
@@ -1,9 +1,9 @@
-import {useTranslations} from 'next-intl';
+import {Locale, useTranslations} from 'next-intl';
 import {setRequestLocale} from 'next-intl/server';
 import PageTitle from '@/components/PageTitle';
 
 type Props = {
-  params: {locale: string};
+  params: {locale: Locale};
 };
 
 export default function About({params: {locale}}: Props) {
diff --git a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/layout.tsx b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/layout.tsx
index 258c83e5f..aca5d3544 100644
--- a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/layout.tsx
+++ b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/layout.tsx
@@ -1,6 +1,6 @@
 import {Metadata} from 'next';
 import {notFound} from 'next/navigation';
-import {NextIntlClientProvider} from 'next-intl';
+import {Locale, NextIntlClientProvider, isValidLocale} from 'next-intl';
 import {getMessages, setRequestLocale} from 'next-intl/server';
 import {ReactNode} from 'react';
 import Document from '@/components/Document';
@@ -10,7 +10,7 @@ import PublicNavigationLocaleSwitcher from './PublicNavigationLocaleSwitcher';
 
 type Props = {
   children: ReactNode;
-  params: {locale: string};
+  params: {locale: Locale};
 };
 
 export function generateStaticParams() {
@@ -25,14 +25,14 @@ export default async function LocaleLayout({
   children,
   params: {locale}
 }: Props) {
-  // Enable static rendering
-  setRequestLocale(locale);
-
   // Ensure that the incoming locale is valid
-  if (!locales.includes(locale as any)) {
+  if (!isValidLocale(locales, locale)) {
     notFound();
   }
 
+  // Enable static rendering
+  setRequestLocale(locale);
+
   // Providing all messages to the client
   // side is the easiest way to get started
   const messages = await getMessages();
diff --git a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/page.tsx b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/page.tsx
index f3ee4cbf4..a12206760 100644
--- a/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/page.tsx
+++ b/examples/example-app-router-mixed-routing/src/app/(public)/[locale]/page.tsx
@@ -1,9 +1,9 @@
-import {useTranslations} from 'next-intl';
+import {Locale, useTranslations} from 'next-intl';
 import {setRequestLocale} from 'next-intl/server';
 import PageTitle from '@/components/PageTitle';
 
 type Props = {
-  params: {locale: string};
+  params: {locale: Locale};
 };
 
 export default function Index({params: {locale}}: Props) {
diff --git a/examples/example-app-router-mixed-routing/src/app/app/AppNavigationLocaleSwitcher.tsx b/examples/example-app-router-mixed-routing/src/app/app/AppNavigationLocaleSwitcher.tsx
index 9101443dc..f85bc3c10 100644
--- a/examples/example-app-router-mixed-routing/src/app/app/AppNavigationLocaleSwitcher.tsx
+++ b/examples/example-app-router-mixed-routing/src/app/app/AppNavigationLocaleSwitcher.tsx
@@ -1,8 +1,7 @@
 'use client';
 
 import {useRouter} from 'next/navigation';
-import {useLocale} from 'next-intl';
-import {Locale} from '@/config';
+import {Locale, useLocale} from 'next-intl';
 import updateLocale from './updateLocale';
 
 export default function AppNavigationLocaleSwitcher() {
diff --git a/examples/example-app-router-mixed-routing/src/config.ts b/examples/example-app-router-mixed-routing/src/config.ts
index d71700814..e7b729aa0 100644
--- a/examples/example-app-router-mixed-routing/src/config.ts
+++ b/examples/example-app-router-mixed-routing/src/config.ts
@@ -1,5 +1,5 @@
+import {Locale} from 'next-intl';
+
 export const locales = ['en', 'de'] as const;
 
 export const defaultLocale: Locale = 'en';
-
-export type Locale = (typeof locales)[number];
diff --git a/examples/example-app-router-mixed-routing/src/db.ts b/examples/example-app-router-mixed-routing/src/db.ts
index 266e9e6a9..44fefcb6e 100644
--- a/examples/example-app-router-mixed-routing/src/db.ts
+++ b/examples/example-app-router-mixed-routing/src/db.ts
@@ -1,5 +1,6 @@
 import {cookies} from 'next/headers';
-import {defaultLocale} from './config';
+import {Locale, isValidLocale} from 'next-intl';
+import {defaultLocale, locales} from './config';
 
 // This cookie name is used by `next-intl` on the public pages too. By
 // reading/writing to this locale, we can ensure that the user's locale
@@ -8,8 +9,9 @@ import {defaultLocale} from './config';
 // that instead when the user is logged in.
 const COOKIE_NAME = 'NEXT_LOCALE';
 
-export async function getUserLocale() {
-  return cookies().get(COOKIE_NAME)?.value || defaultLocale;
+export async function getUserLocale(): Promise<Locale> {
+  const candidate = cookies().get(COOKIE_NAME)?.value;
+  return isValidLocale(locales, candidate) ? candidate : defaultLocale;
 }
 
 export async function setUserLocale(locale: string) {
diff --git a/examples/example-app-router-mixed-routing/src/i18n/request.ts b/examples/example-app-router-mixed-routing/src/i18n/request.ts
index ff3845b6c..62f88c2a6 100644
--- a/examples/example-app-router-mixed-routing/src/i18n/request.ts
+++ b/examples/example-app-router-mixed-routing/src/i18n/request.ts
@@ -1,20 +1,17 @@
+import {isValidLocale} from 'next-intl';
 import {getRequestConfig} from 'next-intl/server';
 import {defaultLocale, locales} from '../config';
 import {getUserLocale} from '../db';
 
 export default getRequestConfig(async ({requestLocale}) => {
   // Read from potential `[locale]` segment
-  let locale = await requestLocale;
+  let candidate = await requestLocale;
 
-  if (!locale) {
+  if (!candidate) {
     // The user is logged in
-    locale = await getUserLocale();
-  }
-
-  // Ensure that the incoming locale is valid
-  if (!locales.includes(locale as any)) {
-    locale = defaultLocale;
+    candidate = await getUserLocale();
   }
+  const locale = isValidLocale(locales, candidate) ? candidate : defaultLocale;
 
   return {
     locale,
diff --git a/examples/example-app-router-next-auth/global.d.ts b/examples/example-app-router-next-auth/global.d.ts
index b749518b9..6f30d7d82 100644
--- a/examples/example-app-router-next-auth/global.d.ts
+++ b/examples/example-app-router-next-auth/global.d.ts
@@ -1,8 +1,10 @@
+import 'next-intl';
+import {routing} from '@/i18n/routing';
 import en from './messages/en.json';
 
-type Messages = typeof en;
-
-declare global {
-  // Use type safe message keys with `next-intl`
-  interface IntlMessages extends Messages {}
+declare module 'next-intl' {
+  interface AppConfig {
+    Locale: (typeof routing.locales)[number];
+    Messages: typeof en;
+  }
 }
diff --git a/examples/example-app-router-next-auth/src/app/[locale]/layout.tsx b/examples/example-app-router-next-auth/src/app/[locale]/layout.tsx
index 0acc48b28..844197840 100644
--- a/examples/example-app-router-next-auth/src/app/[locale]/layout.tsx
+++ b/examples/example-app-router-next-auth/src/app/[locale]/layout.tsx
@@ -1,20 +1,19 @@
 import {notFound} from 'next/navigation';
-import {NextIntlClientProvider} from 'next-intl';
+import {Locale, NextIntlClientProvider, isValidLocale} from 'next-intl';
 import {getMessages} from 'next-intl/server';
 import {ReactNode} from 'react';
 import {routing} from '@/i18n/routing';
 
 type Props = {
   children: ReactNode;
-  params: {locale: string};
+  params: {locale: Locale};
 };
 
 export default async function LocaleLayout({
   children,
   params: {locale}
 }: Props) {
-  // Ensure that the incoming `locale` is valid
-  if (!routing.locales.includes(locale as any)) {
+  if (!isValidLocale(routing.locales, locale)) {
     notFound();
   }
 
diff --git a/examples/example-app-router-next-auth/src/i18n/request.ts b/examples/example-app-router-next-auth/src/i18n/request.ts
index 70066e964..0534cbacd 100644
--- a/examples/example-app-router-next-auth/src/i18n/request.ts
+++ b/examples/example-app-router-next-auth/src/i18n/request.ts
@@ -1,14 +1,13 @@
+import {isValidLocale} from 'next-intl';
 import {getRequestConfig} from 'next-intl/server';
 import {routing} from './routing';
 
 export default getRequestConfig(async ({requestLocale}) => {
-  // This typically corresponds to the `[locale]` segment
-  let locale = await requestLocale;
-
-  // Ensure that the incoming locale is valid
-  if (!locale || !routing.locales.includes(locale as any)) {
-    locale = routing.defaultLocale;
-  }
+  // Typically corresponds to the `[locale]` segment
+  const requested = await requestLocale;
+  const locale = isValidLocale(routing.locales, requested)
+    ? requested
+    : routing.defaultLocale;
 
   return {
     locale,
diff --git a/examples/example-app-router-playground/src/app/[locale]/layout.tsx b/examples/example-app-router-playground/src/app/[locale]/layout.tsx
index 88935f893..0c8f63791 100644
--- a/examples/example-app-router-playground/src/app/[locale]/layout.tsx
+++ b/examples/example-app-router-playground/src/app/[locale]/layout.tsx
@@ -1,6 +1,6 @@
 import {Metadata} from 'next';
 import {notFound} from 'next/navigation';
-import {Locale} from 'next-intl';
+import {Locale, isValidLocale} from 'next-intl';
 import {
   getFormatter,
   getNow,
@@ -36,8 +36,7 @@ export async function generateMetadata({
 }
 
 export default function LocaleLayout({children, params: {locale}}: Props) {
-  // Ensure that the incoming `locale` is valid
-  if (!routing.locales.includes(locale as any)) {
+  if (!isValidLocale(routing.locales, locale)) {
     notFound();
   }
 
diff --git a/examples/example-app-router/global.d.ts b/examples/example-app-router/global.d.ts
index 44f1f8333..9a7bf7165 100644
--- a/examples/example-app-router/global.d.ts
+++ b/examples/example-app-router/global.d.ts
@@ -5,12 +5,7 @@ import en from './messages/en.json';
 declare module 'next-intl' {
   interface AppConfig {
     Locale: (typeof routing.locales)[number];
+    Messages: typeof en;
   }
 }
 
-type Messages = typeof en;
-
-declare global {
-  // Use type safe message keys with `next-intl`
-  interface IntlMessages extends Messages {}
-}
diff --git a/examples/example-pages-router-advanced/global.d.ts b/examples/example-pages-router-advanced/global.d.ts
index b749518b9..094440ccb 100644
--- a/examples/example-pages-router-advanced/global.d.ts
+++ b/examples/example-pages-router-advanced/global.d.ts
@@ -1,8 +1,8 @@
+import 'next-intl';
 import en from './messages/en.json';
 
-type Messages = typeof en;
-
-declare global {
-  // Use type safe message keys with `next-intl`
-  interface IntlMessages extends Messages {}
+declare module 'next-intl' {
+  interface AppConfig {
+    Messages: typeof en;
+  }
 }
diff --git a/examples/example-pages-router-advanced/src/pages/_app.tsx b/examples/example-pages-router-advanced/src/pages/_app.tsx
index 14f75d12d..165d5fcbb 100644
--- a/examples/example-pages-router-advanced/src/pages/_app.tsx
+++ b/examples/example-pages-router-advanced/src/pages/_app.tsx
@@ -1,9 +1,9 @@
 import {AppProps} from 'next/app';
 import {useRouter} from 'next/router';
-import {NextIntlClientProvider} from 'next-intl';
+import {Messages, NextIntlClientProvider} from 'next-intl';
 
 type PageProps = {
-  messages: IntlMessages;
+  messages: Messages;
   now: number;
 };
 
diff --git a/examples/example-pages-router/global.d.ts b/examples/example-pages-router/global.d.ts
index b749518b9..094440ccb 100644
--- a/examples/example-pages-router/global.d.ts
+++ b/examples/example-pages-router/global.d.ts
@@ -1,8 +1,8 @@
+import 'next-intl';
 import en from './messages/en.json';
 
-type Messages = typeof en;
-
-declare global {
-  // Use type safe message keys with `next-intl`
-  interface IntlMessages extends Messages {}
+declare module 'next-intl' {
+  interface AppConfig {
+    Messages: typeof en;
+  }
 }
diff --git a/examples/example-use-intl/global.d.ts b/examples/example-use-intl/global.d.ts
new file mode 100644
index 000000000..5f39e9b68
--- /dev/null
+++ b/examples/example-use-intl/global.d.ts
@@ -0,0 +1,10 @@
+import 'use-intl';
+import en from './messages/en.json';
+import {locales} from './src/config';
+
+declare module 'use-intl' {
+  interface AppConfig {
+    Locale: (typeof locales)[number];
+    Messages: typeof en;
+  }
+}
diff --git a/examples/example-use-intl/messages/en.json b/examples/example-use-intl/messages/en.json
new file mode 100644
index 000000000..51f26812a
--- /dev/null
+++ b/examples/example-use-intl/messages/en.json
@@ -0,0 +1,5 @@
+{
+  "App": {
+    "hello": "Hello {username}!"
+  }
+}
diff --git a/examples/example-use-intl/src/config.tsx b/examples/example-use-intl/src/config.tsx
new file mode 100644
index 000000000..a8a68c781
--- /dev/null
+++ b/examples/example-use-intl/src/config.tsx
@@ -0,0 +1 @@
+export const locales = ['en'] as const;
diff --git a/examples/example-use-intl/src/main.tsx b/examples/example-use-intl/src/main.tsx
index dc772d8ab..d48504350 100644
--- a/examples/example-use-intl/src/main.tsx
+++ b/examples/example-use-intl/src/main.tsx
@@ -1,16 +1,13 @@
 import {StrictMode} from 'react';
 import ReactDOM from 'react-dom/client';
 import {IntlProvider} from 'use-intl';
+import en from '../messages/en.json';
 import App from './App.tsx';
 
 // You can get the messages from anywhere you like. You can also
 // fetch them from within a component and then render the provider
 // along with your app once you have the messages.
-const messages = {
-  App: {
-    hello: 'Hello {username}!'
-  }
-};
+const messages = en;
 
 const node = document.getElementById('root');
 
diff --git a/examples/example-use-intl/tsconfig.json b/examples/example-use-intl/tsconfig.json
index ba939e9e6..799ffcd9d 100644
--- a/examples/example-use-intl/tsconfig.json
+++ b/examples/example-use-intl/tsconfig.json
@@ -13,6 +13,6 @@
     "noEmit": true,
     "jsx": "react-jsx"
   },
-  "include": ["src"],
+  "include": ["**/*.ts", "**/*.tsx"],
   "references": [{"path": "./tsconfig.node.json"}]
 }