diff --git a/composer.json b/composer.json
index 90cc1be..d363f4c 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
         "php": ">=5.2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "4.*"
+        "phpunit/phpunit": "4.*|5.*"
     },
     "suggest": {
         "ext-libsodium": "Provides a modern crypto API that can be used to generate random bytes."