diff --git a/composer.json b/composer.json
index 6149b84..7f866ab 100755
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,8 @@
         }
     ],
     "require": {
-        "phpunit/phpunit": "^5.0 || ^6.0 || ^7.0"
+        "phpunit/phpunit": "^5.0 || ^6.0 || ^7.0",
+        "vimeo/psalm": "^3.0"
     },
     "require-dev": {
         "squizlabs/php_codesniffer": "^3.3"