diff --git a/composer.lock b/composer.lock
index fea8fd95c3ed75b8e27a1218cbf19cda5c7d9632..2cc35dc2c639e25a894dfe6476b2b77f7f35cee6 100644
--- a/composer.lock
+++ b/composer.lock
@@ -457,7 +457,7 @@
         },
         {
             "name": "drupal/core",
-            "version": "9.0.0",
+            "version": "9.0.x-dev",
             "dist": {
                 "type": "path",
                 "url": "core",
@@ -701,7 +701,7 @@
         },
         {
             "name": "drupal/core-project-message",
-            "version": "9.0.0",
+            "version": "9.0.x-dev",
             "dist": {
                 "type": "path",
                 "url": "composer/Plugin/ProjectMessage",
@@ -731,7 +731,7 @@
         },
         {
             "name": "drupal/core-vendor-hardening",
-            "version": "9.0.0",
+            "version": "9.0.x-dev",
             "dist": {
                 "type": "path",
                 "url": "composer/Plugin/VendorHardening",
@@ -4090,6 +4090,9 @@
                 "ext-zip": "Enabling the zip extension allows you to unzip archives",
                 "ext-zlib": "Allow gzip compression of HTTP requests"
             },
+            "bin": [
+                "bin/composer"
+            ],
             "type": "library",
             "extra": {
                 "branch-alias": {
@@ -6560,7 +6563,11 @@
     ],
     "aliases": [],
     "minimum-stability": "dev",
-    "stability-flags": [],
+    "stability-flags": {
+        "drupal/core": 20,
+        "drupal/core-project-message": 20,
+        "drupal/core-vendor-hardening": 20
+    },
     "prefer-stable": true,
     "prefer-lowest": false,
     "platform": [],
diff --git a/composer/Metapackage/CoreRecommended/composer.json b/composer/Metapackage/CoreRecommended/composer.json
index c5aad3c97f3ca5ffde2fe5caf46d2442b0c9a666..a33a957d9fd35eb437053429689d618cf5e02af6 100644
--- a/composer/Metapackage/CoreRecommended/composer.json
+++ b/composer/Metapackage/CoreRecommended/composer.json
@@ -7,7 +7,7 @@
         "webflo/drupal-core-strict": "*"
     },
     "require": {
-        "drupal/core": "9.0.0",
+        "drupal/core": "9.0.x-dev",
         "asm89/stack-cors": "1.3.0",
         "composer/semver": "1.5.1",
         "doctrine/annotations": "1.10.3",
diff --git a/composer/Metapackage/PinnedDevDependencies/composer.json b/composer/Metapackage/PinnedDevDependencies/composer.json
index 2d0a172e6c0a6d37c7bd59ea879c74bcd784542c..0c80dcac811825f647c9bc2c7cce8580f5c870e1 100644
--- a/composer/Metapackage/PinnedDevDependencies/composer.json
+++ b/composer/Metapackage/PinnedDevDependencies/composer.json
@@ -7,7 +7,7 @@
         "webflo/drupal-core-require-dev": "*"
     },
     "require": {
-        "drupal/core": "9.0.0",
+        "drupal/core": "9.0.x-dev",
         "behat/mink": "v1.8.1",
         "behat/mink-browserkit-driver": "v1.3.4",
         "behat/mink-goutte-driver": "v1.2.1",
diff --git a/core/lib/Drupal.php b/core/lib/Drupal.php
index 21e73d9712da453466a1ea9a327332df8ebd8b97..fda499e57d9549c5e2c80740e48d83586dfd796d 100644
--- a/core/lib/Drupal.php
+++ b/core/lib/Drupal.php
@@ -80,7 +80,7 @@ class Drupal {
   /**
    * The current system version.
    */
-  const VERSION = '9.0.0';
+  const VERSION = '9.0.1-dev';
 
   /**
    * Core API compatibility.