diff --git a/composer.json b/composer.json
index eab5651..0325d7d 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,7 @@
     "monolog/monolog": "~1.0|~2.0|~3.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^5.7"
+    "phpunit/phpunit": ">=5.7"
   },
   "autoload": {
     "psr-4": {