diff --git a/CHANGELOG.md b/CHANGELOG.md
index f294f7e..bf702ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.4.0] - 2026-08-20
+
 ### Added
 
 - `spacing` (default `0`): pixels of blank space between the tree panel and
diff --git a/pyproject.toml b/pyproject.toml
index 6c23569..69bc7cf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "tree-annotated-plot"
-version = "0.3.0"
+version = "0.4.0"
 description = "Annotate the axis of an Altair / Vega-Lite plot with a phylogenetic tree."
 readme = "README.md"
 requires-python = ">=3.11"