diff --git a/.env.local.demo b/.env.local.demo
new file mode 100644
index 000000000..d79c676ae
--- /dev/null
+++ b/.env.local.demo
@@ -0,0 +1,3 @@
+# This variable is for the demo app only!
+# See https://symfony.com/doc/current/reference/configuration/framework.html#configuration-framework-secret
+APP_SECRET=not-a-secret--read-the-doc!
diff --git a/composer.json b/composer.json
index aac55c6a9..2574f522e 100644
--- a/composer.json
+++ b/composer.json
@@ -91,6 +91,7 @@
     },
     "scripts": {
         "auto-scripts": {
+            "-r \"@rename('.env.local.demo', '.env.local');\"": "php-script",
             "cache:clear": "symfony-cmd",
             "assets:install %PUBLIC_DIR%": "symfony-cmd",
             "importmap:install": "symfony-cmd",