diff --git a/pyproject.toml b/pyproject.toml
index 1f2942f7e15d56ff0cc1c8780533a52df427a306..8ebf7827bf9932c5b80d2ee2162749bb238e4215 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,6 +9,7 @@ license = {file = "LICENSE"}
 classifiers = ["License :: OSI Approved :: MIT License"]
 version = "2023.6.27"
 readme = "README.rst"
+requires-python = ">=3.9"
 dependencies = [
     "archspec",
     "rich",