diff --git a/composer.json b/composer.json
index f52fd155..235b2af8 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
         "guzzlehttp/psr7": "~1.1"
     },
     "require-dev": {
-        "phpunit/phpunit": "3.*",
+        "phpunit/phpunit": "^4.8 || ^5.7",
         "mockery/mockery": "~0.9.2"
     },
     "suggest": {