diff --git a/composer.json b/composer.json
index 7294446..adc9960 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
         "php": ">=5.5"
     },
     "require-dev": {
-        "phpunit/phpunit":"^4.8.35|^5.6.3"
+        "phpunit/phpunit":"^5.6.3"
     },
     "autoload": {
         "classmap": [