diff --git a/composer.json b/composer.json
index dc80706..bbcda83 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,7 @@
     "darrynten/any-cache": "^1.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "~5.0",
+    "phpunit/phpunit": "~5.0 || ~9.0",
     "mockery/mockery": "dev-master"
   },
   "config": {