diff --git a/etc/Makefile b/etc/Makefile
index 24e54550..314225a8 100644
--- a/etc/Makefile
+++ b/etc/Makefile
@@ -8,5 +8,14 @@ include ${MK}/os.mk
 include Makefile.${OS}
 include ${MK}/scripts.mk
 
+# We can't use "ifndef" here because that treats set-but-empty
+# as not-set which is not what we want
+MKRCSYS ?= automagicplease
+ifeq ($(MKRCSYS),automagicplease)
+# If the user isn't picking a default, then have the
+# config go with runtime automagic detection #357247
+rc.conf: SED_EXTRA += -e '/^rc_sys=""/s:^:\#:'
+MKRCSYS =
+endif
 rc.conf: rc.conf.in rc.conf.${OS}
 	${SED} ${SED_REPLACE} ${SED_EXTRA} $^ > $@