diff --git a/setup.cfg b/setup.cfg
index 56595ebd..35526907 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -32,6 +32,7 @@ classifiers =
 
 [options]
 packages = find:
+python_requires = >=3.9
 install_requires =
     ecdsa != 0.15
     rsa >=4.0, <5.0, !=4.4, !=4.1.1