diff --git a/composer.json b/composer.json
index 7495d22..0dbfa01 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
         "psr-4": {"ShortCode\\": "tests/ShortCode"}
     },
     "require-dev": {
-        "satooshi/php-coveralls": "^1.1",
-        "phpunit/phpunit": "^4.8|^5.5|^6.5"
+        "satooshi/php-coveralls": "^1.1|^2.4.3",
+        "phpunit/phpunit": "^4.8|^5.5|^6.5|^9.0"
     }
 }