diff --git a/symfony/asset-mapper/6.3/assets/app.js b/symfony/asset-mapper/6.4/assets/app.js
index cb0082a..6174cc6 100644
--- a/symfony/asset-mapper/6.3/assets/app.js
+++ b/symfony/asset-mapper/6.4/assets/app.js
@@ -4,4 +4,6 @@
  * This file will be included onto the page via the importmap() Twig function,
  * which should already be in your base.html.twig.
  */
-console.log('This log comes from assets/app.js - welcome to AssetMapper! 🎉')
+import './styles/app.css';
+
+console.log('This log comes from assets/app.js - welcome to AssetMapper! 🎉');
diff --git a/symfony/asset-mapper/6.3/config/packages/asset_mapper.yaml b/symfony/asset-mapper/6.4/config/packages/asset_mapper.yaml
index d1ac653..f7653e9 100644
--- a/symfony/asset-mapper/6.3/config/packages/asset_mapper.yaml
+++ b/symfony/asset-mapper/6.4/config/packages/asset_mapper.yaml
@@ -3,3 +3,9 @@ framework:
         # The paths to make available to the asset mapper.
         paths:
             - assets/
+        missing_import_mode: strict
+
+when@prod:
+    framework:
+        asset_mapper:
+            missing_import_mode: warn
diff --git a/symfony/asset-mapper/6.3/importmap.php b/symfony/asset-mapper/6.4/importmap.php
index 5c2c21d..70ebf14 100644
--- a/symfony/asset-mapper/6.3/importmap.php
+++ b/symfony/asset-mapper/6.4/importmap.php
@@ -1,21 +1,19 @@
 <?php
 
 /**
- * Returns the import map for this application.
+ * Returns the importmap for this application.
  *
  * - "path" is a path inside the asset mapper system. Use the
  *     "debug:asset-map" command to see the full list of paths.
  *
- * - "preload" set to true for any modules that are loaded on the initial
- *     page load to help the browser download them earlier.
+ * - "entrypoint" (JavaScript only) set to true for any module that will
+ *     be used as an "entrypoint" (and passed to the importmap() Twig function).
  *
  * The "importmap:require" command can be used to add new entries to this file.
- *
- * This file has been auto-generated by the importmap commands.
  */
 return [
     'app' => [
-        'path' => 'app.js',
-        'preload' => true,
+        'path' => './assets/app.js',
+        'entrypoint' => true,
     ],
 ];
diff --git a/symfony/asset-mapper/6.3/manifest.json b/symfony/asset-mapper/6.4/manifest.json
index c6fb477..7454a3d 100644
--- a/symfony/asset-mapper/6.3/manifest.json
+++ b/symfony/asset-mapper/6.4/manifest.json
@@ -6,22 +6,19 @@
     },
     "aliases": ["asset-mapper", "importmap"],
     "gitignore": [
-        "/%PUBLIC_DIR%/assets/"
+        "/%PUBLIC_DIR%/assets/",
+        "/assets/vendor/"
     ],
+    "composer-scripts": {
+        "importmap:install": "symfony-cmd"
+    },
     "add-lines": [
         {
             "file": "templates/base.html.twig",
-            "content": "            {{ importmap() }}",
+            "content": "            {% block importmap %}{{ importmap('app') }}{% endblock %}",
             "position": "after_target",
             "target": "{% block javascripts %}",
             "warn_if_missing": true
-        },
-        {
-            "file": "templates/base.html.twig",
-            "content": "            <link rel=\"stylesheet\" href=\"{{ asset('styles/app.css') }}\">",
-            "position": "after_target",
-            "target": "{% block stylesheets %}",
-            "warn_if_missing": true
         }
     ],
     "conflict": {