diff --git a/composer.lock b/composer.lock
index 58295fc987d77ad79d238f680c03166dedc99f9b..8451361f434cd374f31b6204c839c64af5404955 100644
--- a/composer.lock
+++ b/composer.lock
@@ -453,7 +453,7 @@
         },
         {
             "name": "drupal/core",
-            "version": "9.0.x-dev",
+            "version": "9.0.0-beta1",
             "dist": {
                 "type": "path",
                 "url": "core",
@@ -699,7 +699,7 @@
         },
         {
             "name": "drupal/core-project-message",
-            "version": "9.0.x-dev",
+            "version": "9.0.0-beta1",
             "dist": {
                 "type": "path",
                 "url": "composer/Plugin/ProjectMessage",
@@ -729,7 +729,7 @@
         },
         {
             "name": "drupal/core-vendor-hardening",
-            "version": "9.0.x-dev",
+            "version": "9.0.0-beta1",
             "dist": {
                 "type": "path",
                 "url": "composer/Plugin/VendorHardening",
@@ -6538,11 +6538,7 @@
     ],
     "aliases": [],
     "minimum-stability": "dev",
-    "stability-flags": {
-        "drupal/core": 20,
-        "drupal/core-project-message": 20,
-        "drupal/core-vendor-hardening": 20
-    },
+    "stability-flags": [],
     "prefer-stable": true,
     "prefer-lowest": false,
     "platform": [],
diff --git a/composer/Metapackage/CoreRecommended/composer.json b/composer/Metapackage/CoreRecommended/composer.json
index 31e54857efdf18a22728929ef9a34672ecef622c..57cf121d5e824258f6d5dc1f349854f426901f1d 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.x-dev",
+        "drupal/core": "9.0.0-beta1",
         "asm89/stack-cors": "1.3.0",
         "composer/installers": "v1.8.0",
         "composer/semver": "1.5.1",
diff --git a/composer/Metapackage/PinnedDevDependencies/composer.json b/composer/Metapackage/PinnedDevDependencies/composer.json
index 987f92a6ea37d785f14c62ae31353c1dec11b9a4..4baeb6ee1a415c0e6145210db764ee7bc2cd81de 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.x-dev",
+        "drupal/core": "9.0.0-beta1",
         "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 eb155efb0e9da4f59198ae677ca551a3af982ceb..f1e0dab156459e14a3f96c8ef1abe95e59ca5804 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-dev';
+  const VERSION = '9.0.0-beta1';
 
   /**
    * Core API compatibility.