diff --git a/.gitignore b/.gitignore
index 779588ef01d8baa48f0e1d12a92af2d44cf16ccb..b98e6c7343b8f421f275930200643e7fbef25f40 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,8 @@
 # Python object cache
 *.py[co]
 
+# Packages
+*.whl
+
 # Test results
 /results/
diff --git a/pyproject.toml b/pyproject.toml
index 0af961709c977b7d3dbd355d00f9b7a0861a4f8a..bc8068a013e3c40da69a8ccf74f24c904591733a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -10,7 +10,10 @@ authors = [
 license = {file = "LICENCE.txt"}
 readme = "README.md"
 dynamic = ["version", "description"]
-requires-python = "~=3.9"
+
+# https://github.com/pypa/flit/issues/476
+requires-python = ">=3.9,<4"
+
 dependencies = [
 	"jinja2",
 ]