diff --git a/mozilla/tools/tinderbox-configs/lightning/macosx/mozconfig b/mozilla/tools/tinderbox-configs/lightning/macosx/mozconfig
index 672b05efd38..0bbd3a38770 100755
--- a/mozilla/tools/tinderbox-configs/lightning/macosx/mozconfig
+++ b/mozilla/tools/tinderbox-configs/lightning/macosx/mozconfig
@@ -5,7 +5,8 @@
 
 . $topsrcdir/build/macosx/universal/mozconfig
 
-mk_add_options MOZ_POSTFLIGHT_ALL+=calendar/lightning/build/universal.mk
+# Overwrite, because there is no need to package thunderbird itself
+mk_add_options MOZ_POSTFLIGHT_ALL=calendar/lightning/build/universal.mk
 
 mk_add_options MOZ_CO_PROJECT=mail,calendar
 mk_add_options MOZ_MAKE_FLAGS="-j4"