diff --git a/composer.json b/composer.json
index 7f866ab..344abbf 100755
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,7 @@
     ],
     "require": {
         "phpunit/phpunit": "^5.0 || ^6.0 || ^7.0",
-        "vimeo/psalm": "^3.0"
+        "vimeo/psalm": "^3.0 || dev-master"
     },
     "require-dev": {
         "squizlabs/php_codesniffer": "^3.3"