diff --git a/mozilla/calendar/lightning/moz.build b/mozilla/calendar/lightning/moz.build
index 4de8451..984efca 100644
--- a/mozilla/calendar/lightning/moz.build
+++ b/mozilla/calendar/lightning/moz.build
@@ -7,6 +7,7 @@ DIRS += [
     '../libical',
     '../base',
     '../providers',
+    '../timezones',
     '../import-export',
     '../itip',
     'components',