diff --git a/packages/ubuntu_localizations/lib/src/localizations.dart b/packages/ubuntu_localizations/lib/src/localizations.dart
index 4aedff93..ad172205 100644
--- a/packages/ubuntu_localizations/lib/src/localizations.dart
+++ b/packages/ubuntu_localizations/lib/src/localizations.dart
@@ -30,7 +30,10 @@ class GlobalUbuntuLocalizations {
 /// * [Intl.defaultLocale]
 /// * [Intl.systemLocale]
 Future<void> initDefaultLocale([String? locale]) async {
-  Intl.defaultLocale = locale ?? await findSystemLocale();
+  Intl.defaultLocale = locale ??
+      await findSystemLocale()
+          // Fallback to 'en' if the system locale is 'POSIX' or undefined.
+          .then((l) => l == 'POSIX' || l == 'und' ? 'en' : l);
 }
 
 /// A localized language and its locale.