diff --git a/package-lock.json b/package-lock.json
index 9a50ca4..0bce3b3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "web-streams-polyfill",
-  "version": "3.1.1",
+  "version": "4.0.0-beta.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 080024c..8b962d0 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "web-streams-polyfill",
-  "version": "3.1.1",
+  "version": "4.0.0-beta.1",
   "description": "Web Streams, based on the WHATWG spec reference implementation",
   "main": "dist/ponyfill.js",
   "module": "dist/ponyfill.mjs",