Index: pyproject.toml
--- pyproject.toml.orig
+++ pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core >=3.2.0,<4"]
+requires = ["flit_core >=3.2.0"]
 build-backend = "flit_core.buildapi"
 
 [project]
