diff --git a/composer.json b/composer.json
index ce28838..59bdad1 100644
--- a/composer.json
+++ b/composer.json
@@ -8,7 +8,7 @@
     },
     "require-dev": {
         "gecko-packages/gecko-php-unit": "^2.0",
-        "phpunit/phpunit": "^6.0",
+        "phpunit/phpunit": "^6.0 || ^8.0",
         "friendsofphp/php-cs-fixer": "2.16.3"
     },
     "autoload": {