diff --git a/ts/test-node/util/resolveCanonicalLocales_test.ts b/ts/test-node/util/resolveCanonicalLocales_test.ts
new file mode 100644
index 00000000000..273a46ce863
--- /dev/null
+++ b/ts/test-node/util/resolveCanonicalLocales_test.ts
@@ -0,0 +1,22 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import assert from 'node:assert/strict';
+import { resolveCanonicalLocales } from '../../util/resolveCanonicalLocales';
+
+describe('resolveCanonicalLocales', () => {
+  it('returns an array of canonical locales', () => {
+    assert.deepEqual(
+      resolveCanonicalLocales(['EN', 'EN-US', 'EN-GB', 'FR', 'FR-FR']),
+      ['en', 'en-US', 'en-GB', 'fr', 'fr-FR']
+    );
+  });
+
+  it('removes invalid locales', () => {
+    assert.deepEqual(resolveCanonicalLocales(['!@#$', 'POSIX', 'en']), ['en']);
+  });
+
+  it('defaults to en if no valid locales are provided', () => {
+    assert.deepEqual(resolveCanonicalLocales(['!@#$']), ['en']);
+  });
+});
diff --git a/ts/util/resolveCanonicalLocales.ts b/ts/util/resolveCanonicalLocales.ts
index 3517f582004..f52d999467b 100644
--- a/ts/util/resolveCanonicalLocales.ts
+++ b/ts/util/resolveCanonicalLocales.ts
@@ -2,13 +2,18 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 export function resolveCanonicalLocales(locales: Array<string>): Array<string> {
-  return Intl.getCanonicalLocales(
-    locales.flatMap(locale => {
-      try {
-        return Intl.getCanonicalLocales(locale);
-      } catch {
-        return 'en';
-      }
-    })
-  );
+  const validLocales = locales.filter(locale => {
+    try {
+      // Test if the locale is valid
+      new Intl.Locale(locale).maximize();
+      return true;
+    } catch {
+      return false;
+    }
+  });
+  const canonical = Intl.getCanonicalLocales(validLocales);
+  if (canonical.length === 0) {
+    return ['en'];
+  }
+  return canonical;
 }