diff --git a/CHANGELOG.md b/CHANGELOG.md
index f16cb25..96d18b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,16 @@
 # Release notes
 
+## 0.4.0 (2024-04-08)
+
+### Miscellaneous Tasks
+
+- [**breaking**] Update pyo3 to 0.21 ([#33](https://github.com/CQCL/tket-json-rs/pull/33))
+
+### Refactor
+
+- Move `OpBox` to a new module ([#35](https://github.com/CQCL/tket-json-rs/pull/35))
+
+
 ## 0.3.1 (2024-02-26)
 
 ### Features
diff --git a/Cargo.toml b/Cargo.toml
index c60adbe..3e97246 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "tket-json-rs"
-version = "0.3.1"
+version = "0.4.0"
 license = "Apache-2.0"
 edition = "2021"
 rust-version = "1.70"