diff --git a/pkgs/development/python-modules/rx/default.nix b/pkgs/development/python-modules/rx/default.nix
index 5eeadcdd6244..3102568bcb82 100644
--- a/pkgs/development/python-modules/rx/default.nix
+++ b/pkgs/development/python-modules/rx/default.nix
@@ -3,12 +3,14 @@
   fetchPypi,
   buildPythonPackage,
   pythonOlder,
+  setuptools,
 }:
 
 buildPythonPackage rec {
   pname = "rx";
   version = "3.2.0";
-  format = "setuptools";
+  pyproject = true;
+
   disabled = pythonOlder "3.6";
 
   # Use fetchPypi to avoid the updater script to migrate it to `reactivex` which
@@ -19,6 +21,8 @@ buildPythonPackage rec {
     sha256 = "b657ca2b45aa485da2f7dcfd09fac2e554f7ac51ff3c2f8f2ff962ecd963d91c";
   };
 
+  build-system = [ setuptools ];
+
   doCheck = false; # PyPI tarball does not provides tests
 
   pythonImportsCheck = [ "rx" ];