diff --git a/composer.json b/composer.json
index 8073483..8e6f27c 100755
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
         "silverstripe/tagfield": "^1.0"
     },
     "require-dev": {
-        "phpunit/PHPUnit": "~3.7@stable"
+        "phpunit/phpunit": "^5.7"
     },
     "extra": [],
     "license": "BSD-2-Clause",