diff --git a/composer.json b/composer.json
index 664c8eb0..bb478f57 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,8 @@
         "phpunit/phpunit": "^4.8.36 || ^7.5.13"
     },
     "conflict": {
-        "vimeo/psalm": "<3.9.1"
+        "vimeo/psalm": "<3.9.1",
+        "phpstan/phpstan": "<0.12.20"
     },
     "autoload": {
         "psr-4": {