diff --git a/composer.json b/composer.json
index 1e9414c..9f7d4f1 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
         "arbiter/arbiter": "~1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.1",
+        "phpunit/phpunit": "^7.1 || ^8.0",
         "laminas/laminas-diactoros":    "~2.2"
     },
     "autoload": {