diff --git a/packages/next-intl/src/routing/defineRouting.tsx b/packages/next-intl/src/routing/defineRouting.tsx
index b975a519f..1b34187ce 100644
--- a/packages/next-intl/src/routing/defineRouting.tsx
+++ b/packages/next-intl/src/routing/defineRouting.tsx
@@ -5,6 +5,7 @@ import type {
   Locales,
   Pathnames
 } from './types.tsx';
+import validateLocales from './validateLocales.tsx';
 
 export default function defineRouting<
   const AppLocales extends Locales,
@@ -19,5 +20,8 @@ export default function defineRouting<
     AppDomains
   >
 ) {
+  if (process.env.NODE_ENV !== 'production') {
+    validateLocales(config.locales);
+  }
   return config;
 }
diff --git a/packages/next-intl/src/routing/validateLocales.test.tsx b/packages/next-intl/src/routing/validateLocales.test.tsx
new file mode 100644
index 000000000..5e6d0f851
--- /dev/null
+++ b/packages/next-intl/src/routing/validateLocales.test.tsx
@@ -0,0 +1,71 @@
+import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
+import validateLocales from './validateLocales.tsx';
+
+describe('accepts valid formats', () => {
+  let consoleErrorSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    consoleErrorSpy.mockRestore();
+  });
+
+  it.each([
+    'en',
+    'en-US',
+    'EN-US',
+    'en-us',
+    'en-GB',
+    'zh-Hans-CN',
+    'es-419',
+    'en-Latn',
+    'zh-Hans',
+    'en-US-u-ca-buddhist',
+    'en-x-private1',
+    'en-US-u-nu-thai',
+    'ar-u-nu-arab',
+    'en-t-m0-true',
+    'zh-Hans-CN-x-private1-private2',
+    'en-US-u-ca-gregory-nu-latn',
+    'en-US-x-usd',
+
+    // Somehow tolerated by Intl.Locale
+    'english'
+  ])('accepts: %s', (locale) => {
+    validateLocales([locale]);
+    expect(consoleErrorSpy).not.toHaveBeenCalled();
+  });
+});
+
+describe('warns for invalid formats', () => {
+  let consoleErrorSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    consoleErrorSpy.mockRestore();
+  });
+
+  it.each([
+    'en_US',
+    'en-',
+    'e-US',
+    'en-USA',
+    'und',
+    '123',
+    '-en',
+    'en--US',
+    'toolongstring',
+    'en-US-',
+    '@#$',
+    'en US',
+    'en.US'
+  ])('rejects: %s', (locale) => {
+    validateLocales([locale]);
+    expect(consoleErrorSpy).toHaveBeenCalled();
+  });
+});
diff --git a/packages/next-intl/src/routing/validateLocales.tsx b/packages/next-intl/src/routing/validateLocales.tsx
new file mode 100644
index 000000000..ba09f20b7
--- /dev/null
+++ b/packages/next-intl/src/routing/validateLocales.tsx
@@ -0,0 +1,16 @@
+import type {Locales} from './types.tsx';
+
+export default function validateLocales(locales: Locales) {
+  for (const locale of locales) {
+    try {
+      const constructed = new Intl.Locale(locale);
+      if (!constructed.language) {
+        throw new Error('Language is required');
+      }
+    } catch {
+      console.error(
+        `Found invalid locale within provided \`locales\`: "${locale}"\nPlease ensure you're using a valid Unicode locale identifier (e.g. "en-US").`
+      );
+    }
+  }
+}
diff --git a/packages/use-intl/src/core/hasLocale.test.tsx b/packages/use-intl/src/core/hasLocale.test.tsx
index 19a6dfdcb..713260179 100644
--- a/packages/use-intl/src/core/hasLocale.test.tsx
+++ b/packages/use-intl/src/core/hasLocale.test.tsx
@@ -1,4 +1,4 @@
-import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
+import {it} from 'vitest';
 import hasLocale from './hasLocale.tsx';
 
 it('narrows down the type', () => {
@@ -24,72 +24,3 @@ it('can be called with a non-matching narrow candidate', () => {
     candidate satisfies never;
   }
 });
-
-describe('accepts valid formats', () => {
-  let consoleErrorSpy: ReturnType<typeof vi.spyOn>;
-
-  beforeEach(() => {
-    consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
-  });
-
-  afterEach(() => {
-    consoleErrorSpy.mockRestore();
-  });
-
-  it.each([
-    'en',
-    'en-US',
-    'EN-US',
-    'en-us',
-    'en-GB',
-    'zh-Hans-CN',
-    'es-419',
-    'en-Latn',
-    'zh-Hans',
-    'en-US-u-ca-buddhist',
-    'en-x-private1',
-    'en-US-u-nu-thai',
-    'ar-u-nu-arab',
-    'en-t-m0-true',
-    'zh-Hans-CN-x-private1-private2',
-    'en-US-u-ca-gregory-nu-latn',
-    'en-US-x-usd',
-
-    // Somehow tolerated by Intl.Locale
-    'english'
-  ])('accepts: %s', (locale) => {
-    expect(hasLocale([locale] as const, locale)).toBe(true);
-    expect(consoleErrorSpy).not.toHaveBeenCalled();
-  });
-});
-
-describe('warns for invalid formats', () => {
-  let consoleErrorSpy: ReturnType<typeof vi.spyOn>;
-
-  beforeEach(() => {
-    consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
-  });
-
-  afterEach(() => {
-    consoleErrorSpy.mockRestore();
-  });
-
-  it.each([
-    'en_US',
-    'en-',
-    'e-US',
-    'en-USA',
-    'und',
-    '123',
-    '-en',
-    'en--US',
-    'toolongstring',
-    'en-US-',
-    '@#$',
-    'en US',
-    'en.US'
-  ])('rejects: %s', (locale) => {
-    hasLocale([locale] as const, locale);
-    expect(consoleErrorSpy).toHaveBeenCalled();
-  });
-});
diff --git a/packages/use-intl/src/core/hasLocale.tsx b/packages/use-intl/src/core/hasLocale.tsx
index 6094cfd01..5bb68714c 100644
--- a/packages/use-intl/src/core/hasLocale.tsx
+++ b/packages/use-intl/src/core/hasLocale.tsx
@@ -3,29 +3,11 @@ import type {Locale} from './AppConfig.tsx';
 /**
  * Checks if a locale exists in a list of locales.
  *
- * Additionally, in development, the provided locales are validated to
- * ensure they follow the Unicode language identifier standard.
- *
  * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale
  */
 export default function hasLocale<LocaleType extends Locale>(
   locales: ReadonlyArray<LocaleType>,
   candidate?: string | null
 ): candidate is LocaleType {
-  if (process.env.NODE_ENV !== 'production') {
-    for (const locale of locales) {
-      try {
-        const constructed = new Intl.Locale(locale);
-        if (!constructed.language) {
-          throw new Error('Language is required');
-        }
-      } catch {
-        console.error(
-          `Found invalid locale within provided \`locales\`: "${locale}"\nPlease ensure you're using a valid Unicode locale identifier (e.g. "en-US").`
-        );
-      }
-    }
-  }
-
   return locales.includes(candidate as LocaleType);
 }