diff --git a/composer.json b/composer.json
index 36c1c2d..cb3e143 100644
--- a/composer.json
+++ b/composer.json
@@ -23,10 +23,11 @@
         }
     },
     "require": {
-        "php": ">=5.4"
+        "php": ">=5.4",
+        "ext-ctype": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^6.5 || ^7.5"
+        "phpunit/phpunit": "^6.5 || ^7.5 || ^8.5"
     },
     "scripts": {
         "test": "phpunit",