diff --git a/pkgs/development/python-modules/tinyio/default.nix b/pkgs/development/python-modules/tinyio/default.nix
index 13f887fdf00d..17f65f9e691a 100644
--- a/pkgs/development/python-modules/tinyio/default.nix
+++ b/pkgs/development/python-modules/tinyio/default.nix
@@ -12,16 +12,16 @@
   trio,
 }:
 
-buildPythonPackage rec {
+buildPythonPackage (finalAttrs: {
   pname = "tinyio";
-  version = "0.3.0";
+  version = "0.4.0";
   pyproject = true;
 
   src = fetchFromGitHub {
     owner = "patrick-kidger";
     repo = "tinyio";
-    tag = "v${version}";
-    hash = "sha256-zAmsUe1fQeTxv0U++lU6abaP8YQMLlF3rkI7eyhTK0I=";
+    tag = "v${finalAttrs.version}";
+    hash = "sha256-a1EbgFcyWz0aihX16ZQbcAwKKneUe+b8qV0cHyMchVI=";
   };
 
   build-system = [
@@ -44,8 +44,8 @@ buildPythonPackage rec {
   meta = {
     description = "Dead-simple event loop for Python";
     homepage = "https://github.com/patrick-kidger/tinyio";
-    changelog = "https://github.com/patrick-kidger/tinyio/releases/tag/${src.tag}";
+    changelog = "https://github.com/patrick-kidger/tinyio/releases/tag/${finalAttrs.src.tag}";
     license = lib.licenses.asl20;
     maintainers = with lib.maintainers; [ GaetanLepage ];
   };
-}
+})