diff --git a/README.md b/README.md
index 052fd55..3fcaf79 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,7 @@ Execute `npm run init` to install/update the development environment and `npm ru
 
 -   Visual Studio Code
 -   Node.js 22.x or later
+-   pnpm 9.x
 
 ### Example `launch.json`
 
diff --git a/package.json b/package.json
index 2a88176..fa71e17 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
     "type": "module",
     "engines": {
         "node": ">=22",
-        "pnpm": ">=8"
+        "pnpm": "9"
     },
     "devDependencies": {
         "@typescript-eslint/eslint-plugin": "^7.16.1",