diff --git a/composer.json b/composer.json
index 3aa0f9a..44fe6ef 100755
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,7 @@
         }
     ],
     "require": {
-        "phpunit/phpunit": "^6.0 || ^7.0 || ^8.0",
+        "phpunit/phpunit": "^6.0 || ^7.0 || ^8.0 || ^9.0",
         "vimeo/psalm": "^3.6.2 || dev-master",
         "composer/semver": "^1.4",
         "ocramius/package-versions": "^1.3"