diff --git a/setup.cfg b/setup.cfg
index df9ef8d1..3fe4541d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -29,6 +29,7 @@ packages = find:
 install_requires =
     packaging>=20.0
     setuptools
+    tomli>=1.0.0 # keep in sync
 python_requires = >=3.6
 package_dir =
     =src