diff --git a/composer.json b/composer.json
index 7e1ca42..025d2aa 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,7 @@
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.11",
-        "phpunit/phpunit": "^5.7",
+        "phpunit/phpunit": "^5.7 || ^9.0",
         "symfony/var-dumper": "^3.4"
     },
     "autoload": {