diff --git a/composer.json b/composer.json
index 6c8305b..2229d3e 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     "phpunit/php-timer": "^2.0||^3.0||^4.0||^5.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^7.0||^8.0||^9.0",
+    "phpunit/phpunit": "^7.5.20||^8.5||^9.0",
     "squizlabs/php_codesniffer": "^2.8.1||^3.5"
   },
   "autoload": {