diff --git a/flags_country/src/Controller/CountryFlagAutocompleteController.php b/flags_country/src/Controller/CountryFlagAutocompleteController.php
index f603cf7..78042d1 100644
--- a/flags_country/src/Controller/CountryFlagAutocompleteController.php
+++ b/flags_country/src/Controller/CountryFlagAutocompleteController.php
@@ -31,7 +31,7 @@ class CountryFlagAutocompleteController extends CountryAutocompleteController {
       $field_definition = FieldConfig::loadByName($entity_type, $bundle, $field_name);
       $countries = \Drupal::service('country.field.manager')->getSelectableCountries($field_definition);
       foreach ($countries as $iso2 => $country) {
-        if (strpos(Unicode::strtolower($country), Unicode::strtolower($string)) !== FALSE) {
+        if (strpos(mb_strtolower($country), mb_strtolower($string)) !== FALSE) {
           $label = array(
             'country' => array('#markup' => $country),
             'flag' => array(