diff --git a/docs/source/_static/rest-api.yml b/docs/source/_static/rest-api.yml
index 1edeeffa..cbc4cc45 100644
--- a/docs/source/_static/rest-api.yml
+++ b/docs/source/_static/rest-api.yml
@@ -6,7 +6,7 @@ info:
   description: The REST API for JupyterHub
   license:
     name: BSD-3-Clause
-  version: 3.2.0.dev
+  version: 4.0.0b1
 servers:
   - url: /hub/api
 security:
diff --git a/jupyterhub/_version.py b/jupyterhub/_version.py
index b6aa3a7c..8bc00b9f 100644
--- a/jupyterhub/_version.py
+++ b/jupyterhub/_version.py
@@ -2,7 +2,7 @@
 # Copyright (c) Jupyter Development Team.
 # Distributed under the terms of the Modified BSD License.
 # version_info updated by running `tbump`
-version_info = (3, 2, 0, "", "dev")
+version_info = (4, 0, 0, "b1", "")
 
 # pep 440 version: no dot before beta/rc, but before .dev
 # 0.1.0rc1
diff --git a/pyproject.toml b/pyproject.toml
index afeb3743..ce81949c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,7 +43,7 @@ target_version = [
 github_url = "https://github.com/jupyterhub/jupyterhub"
 
 [tool.tbump.version]
-current = "3.2.0.dev"
+current = "4.0.0b1"
 
 # Example of a semver regexp.
 # Make sure this matches current_version before