diff --git a/lib/utils/boot.html b/lib/utils/boot.html
index 3ca20b3b7e..0af42f5d9e 100644
--- a/lib/utils/boot.html
+++ b/lib/utils/boot.html
@@ -49,7 +49,7 @@
   };
   /* eslint-enable */
 
-  window.Polymer.version = '2.3.1';
+  window.Polymer.version = '2.4.0-rc.1';
 
   /* eslint-disable no-unused-vars */
   /*
diff --git a/package-lock.json b/package-lock.json
index 4399f788c3..e1c1170505 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "@polymer/polymer",
-  "version": "2.3.1",
+  "version": "2.4.0-rc.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index a1a6673d43..7ba5ea18d1 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polymer/polymer",
-  "version": "2.3.1",
+  "version": "2.4.0-rc.1",
   "description": "The Polymer library makes it easy to create your own web components. Give your element some markup and properties, and then use it on a site. Polymer provides features like dynamic templates and data binding to reduce the amount of boilerplate you need to write",
   "main": "polymer.html",
   "directories": {