--- marshmallow-4.3.1/pyproject.toml.orig
+++ marshmallow-4.3.1/pyproject.toml
@@ -58,7 +58,7 @@
 exclude-newer = "1 week"
 
 [build-system]
-requires = ["flit_core>=3.12,<4"]
+requires = ["flit_core>=3.12"]
 build-backend = "flit_core.buildapi"
 
 [tool.flit.sdist]