diff --git a/pkgs/development/python-modules/tinycss2/default.nix b/pkgs/development/python-modules/tinycss2/default.nix
index 4c21305ac09..35c8578cab4 100644
--- a/pkgs/development/python-modules/tinycss2/default.nix
+++ b/pkgs/development/python-modules/tinycss2/default.nix
@@ -10,7 +10,7 @@
 buildPythonPackage rec {
   pname = "tinycss2";
   version = "1.1.1";
-  format = "flit";
+  format = "pyproject";
 
   disabled = pythonOlder "3.6";