diff --git a/composer.json b/composer.json
index 32b824f3..00573fd7 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
   "require-dev": {
     "dms/phpunit-arraysubset-asserts": "0.5.0",
     "friendsofphp/php-cs-fixer": "*",
-    "phpunit/phpunit": "9.6.19",
+    "phpunit/phpunit": "9.6.21",
     "php-coveralls/php-coveralls": "2.7.0",
     "squizlabs/php_codesniffer": "3.10.2"
   },