diff --git a/pkgs/development/python-modules/pytest-cases/default.nix b/pkgs/development/python-modules/pytest-cases/default.nix
index d4c7b43a2d87..bbc67a278855 100644
--- a/pkgs/development/python-modules/pytest-cases/default.nix
+++ b/pkgs/development/python-modules/pytest-cases/default.nix
@@ -11,7 +11,7 @@
 buildPythonPackage rec {
   pname = "pytest-cases";
   version = "3.8.1";
-  format = "setuptools";
+  pyproject = true;
 
   disabled = pythonOlder "3.6";
 
@@ -33,11 +33,6 @@ buildPythonPackage rec {
     makefun
   ];
 
-  postPatch = ''
-    substituteInPlace setup.cfg \
-      --replace "pytest-runner" ""
-  '';
-
   # Tests have dependencies (pytest-harvest, pytest-steps) which
   # are not available in Nixpkgs. Most of the packages (decopatch,
   # makefun, pytest-*) have circular dependencies.