diff --git a/setup.cfg b/setup.cfg
index e5e2e69..01033b1 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -9,3 +9,6 @@ long_description_content_type = text/markdown
 license_files = LICENSE, COPYRIGHT
 classifiers =
   Programming Language :: Python :: 3
+
+[options]
+python_requires = ~=3.9