diff --git a/pkgs/development/python-modules/mock/default.nix b/pkgs/development/python-modules/mock/default.nix
index 23aff9befea6..9cf7a46fc8ea 100644
--- a/pkgs/development/python-modules/mock/default.nix
+++ b/pkgs/development/python-modules/mock/default.nix
@@ -3,18 +3,21 @@
   buildPythonPackage,
   fetchPypi,
   pytestCheckHook,
+  setuptools,
 }:
 
-buildPythonPackage rec {
+buildPythonPackage (finalAttrs: {
   pname = "mock";
   version = "5.2.0";
-  format = "setuptools";
+  pyproject = true;
 
   src = fetchPypi {
-    inherit pname version;
+    inherit (finalAttrs) pname version;
     hash = "sha256-TkYOgYYptLFz8y0IvzDTr4Ejr7uOBLtXB6H9R5nlA/A=";
   };
 
+  build-system = [ setuptools ];
+
   nativeCheckInputs = [ pytestCheckHook ];
 
   pythonImportsCheck = [ "mock" ];
@@ -22,8 +25,8 @@ buildPythonPackage rec {
   meta = {
     description = "Rolling backport of unittest.mock for all Pythons";
     homepage = "https://github.com/testing-cabal/mock";
-    changelog = "https://github.com/testing-cabal/mock/blob/${version}/CHANGELOG.rst";
+    changelog = "https://github.com/testing-cabal/mock/blob/${finalAttrs.version}/CHANGELOG.rst";
     license = lib.licenses.bsd2;
     maintainers = [ ];
   };
-}
+})