diff --git a/composer.json b/composer.json
index 62fef12..09484a1 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
     ],
     "require": {
         "php": ">=5.4.0",
-        "phpunit/phpunit": "~4.0"
+        "phpunit/phpunit": "^4.0|^5.0"
     },
     "autoload": {
         "psr-0": { "Humbug\\": "src/" }