diff --git a/composer.json b/composer.json
index 24f7383..21eed4e 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
   "require-dev": {
     "ergebnis/composer-normalize": "2.23.1",
     "phpstan/phpstan": "1.4.6",
-    "phpunit/phpunit": "8.5.23",
+    "phpunit/phpunit": "9.5.13",
     "roave/security-advisories": "dev-latest"
   },
   "autoload": {