diff --git a/composer.json b/composer.json
index 15fb107..ed67366 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
         "psr/http-message": "^1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.0"
+        "phpunit/phpunit": "^8.3"
     },
     "autoload": {
         "psr-4": {