diff --git a/pkgs/development/python-modules/csscompressor/default.nix b/pkgs/development/python-modules/csscompressor/default.nix
index 2f3056a98fe4..3936baf4e8f8 100644
--- a/pkgs/development/python-modules/csscompressor/default.nix
+++ b/pkgs/development/python-modules/csscompressor/default.nix
@@ -3,18 +3,21 @@
   buildPythonPackage,
   fetchPypi,
   pytestCheckHook,
+  setuptools,
 }:
 
 buildPythonPackage rec {
   pname = "csscompressor";
   version = "0.9.5";
-  format = "setuptools";
+  pyproject = true;
 
   src = fetchPypi {
     inherit pname version;
     sha256 = "afa22badbcf3120a4f392e4d22f9fff485c044a1feda4a950ecc5eba9dd31a05";
   };
 
+  build-system = [ setuptools ];
+
   nativeCheckInputs = [ pytestCheckHook ];
 
   meta = {