diff --git a/pkgs/development/python-modules/sphinx-external-toc/default.nix b/pkgs/development/python-modules/sphinx-external-toc/default.nix
index cc0163ba3d6..0aff8f37caa 100644
--- a/pkgs/development/python-modules/sphinx-external-toc/default.nix
+++ b/pkgs/development/python-modules/sphinx-external-toc/default.nix
@@ -12,7 +12,7 @@ buildPythonPackage rec {
   pname = "sphinx-external-toc";
   version = "0.3.1";
 
-  format = "flit";
+  format = "pyproject";
 
   disabled = pythonOlder "3.7";