diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 12ce07f..ef0a5a8 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -150,7 +150,7 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php-versions }}
-          extensions: ctype, date, filter, pcre, spl
+          extensions: ctype, date, filter, intl, pcre, spl
           tools: composer
           ini-values: error_reporting=E_ALL
           coverage: pcov
diff --git a/composer.json b/composer.json
index aa5ae8a..a2d241e 100644
--- a/composer.json
+++ b/composer.json
@@ -23,6 +23,8 @@
         "webmozart/assert": "^1.11"
     },
     "require-dev": {
+        "ext-intl": "*",
+
         "simplesamlphp/simplesamlphp-test-framework": "^1.7"
     },
     "autoload": {