diff --git a/setup.cfg b/setup.cfg
index 9d52dfa..805aa44 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -48,6 +48,7 @@ install_requires =
     importlib_metadata; python_version<'3.8'
     cached_property
     camb>=1.0.0
+    packaging
 
 [options.packages.find]
 where = src