diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e1040d..903cb02 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,10 @@
 # Changelog
 All notable changes to this project will be documented in this file.
 
-## [Unreleased]
+## Unreleased
+- None
+
+## [v4.0] - 2021-12-22
 
 ### Added
 - New implementation using the C++ parallel STL (C++17).