diff --git a/composer.json b/composer.json
index f69c1aa..ce2970a 100755
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,7 @@
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.16",
-        "phpunit/phpunit": "^8.0.0"
+        "phpunit/phpunit": "^9.0.0"
     },
     "suggest": {
         "ext-mbstring": "If ext-mbstring is not available you MUST install symfony/polyfill-mbstring"