diff --git a/user/extensions.py b/user/extensions.py
index a8b0394..87772cf 100644
--- a/user/extensions.py
+++ b/user/extensions.py
@@ -18,4 +18,6 @@ import locale
 locale.setlocale(locale.LC_ALL, '')
 
 import weewx.units
+
 weewx.units.obs_group_dict['soilMoist1'] = 'group_percent'
+weewx.units.obs_group_dict['luminosity'] = 'group_illuminance'