diff --git a/CHANGELOG.md b/CHANGELOG.md
index 566cb28..d6b720b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,7 +5,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [DEV]
+## [4.0.0] - 2024-08-09
+
+### Changed
 
 - Include `pycasreg` in source repo to avoid bumping version dominoes
 - Include `lxmlh` in source repo to avoid bumping version dominoes
diff --git a/pyecospold/__init__.py b/pyecospold/__init__.py
index f31a216..d845aad 100644
--- a/pyecospold/__init__.py
+++ b/pyecospold/__init__.py
@@ -16,7 +16,7 @@
     "Defaults",
 )
 
-__version__ = "3.6.2"
+__version__ = "4.0.0"
 
 from .config import Defaults
 from .core import (