diff --git a/CHANGELOG.md b/CHANGELOG.md
index 01d49fe..b1b988a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Changelog
 
-## Unreleased
+## v0.4.0 - 2023-09-11
 
 - Argamak now requires Gleam v0.30 or later.
 - The `tensor` module gains the `concat` slicing/joining function.
diff --git a/README.md b/README.md
index c912279..827afee 100644
--- a/README.md
+++ b/README.md
@@ -32,7 +32,7 @@ $ gleam add argamak
 ```elixir
 defp deps do
   [
-    {:argamak, "~> 0.3"},
+    {:argamak, "~> 0.4"},
   ]
 end
 ```
@@ -43,7 +43,7 @@ end
 
 ```erlang
 {deps, [
-  {argamak, "0.3.0"}
+  {argamak, "0.4.0"}
 ]}.
 ```
 
diff --git a/gleam.toml b/gleam.toml
index c1962b1..2c5ed71 100644
--- a/gleam.toml
+++ b/gleam.toml
@@ -1,5 +1,5 @@
 name = "argamak"
-version = "0.4.0-dev"
+version = "0.4.0"
 description = "A tensor library for the Gleam programming language"
 licences = ["Apache-2.0"]
 gleam = "~> 0.30"