diff --git a/Localization/Localization.php b/Localization/Localization.php
index 4fd894cd3..3982f65a4 100644
--- a/Localization/Localization.php
+++ b/Localization/Localization.php
@@ -220,6 +220,8 @@ class Localization
      */
     public function setLanguage(string $language) /* : void */
     {
+        $language = strtolower($language);
+        
         if (!ISO639x1Enum::isValidValue($language)) {
             throw new InvalidEnumValue($language);
         }