diff --git a/composer.json b/composer.json
index b38de180..3a4eec50 100644
--- a/composer.json
+++ b/composer.json
@@ -46,7 +46,7 @@
         "kelunik/link-header-rfc5988": "^1.0",
         "clue/socks-react": "^1.0",
         "amphp/react-adapter": "^2.1",
-        "vimeo/psalm": "^5",
+        "vimeo/psalm": "~5.20.0",
         "laminas/laminas-diactoros": "^2.3"
     },
     "suggest": {