diff --git a/iterator/iter_hints.c b/iterator/iter_hints.c
index 577ae50b4..36ed999f2 100644
--- a/iterator/iter_hints.c
+++ b/iterator/iter_hints.c
@@ -257,6 +257,9 @@ read_stubs(struct iter_hints* hints, struct config_file* cfg)
 			!read_stubs_host(s, dp) ||
 			!read_stubs_addr(s, dp))
 			return 0;
+		/* the flag is turned off for 'stub-first' so that the
+		 * last resort will ask for parent-side NS record and thus
+		 * fallback to the internet name servers on a failure */
 		dp->has_parent_side_NS = !s->isfirst;
 		if(!hints_insert(hints, LDNS_RR_CLASS_IN, dp, !s->isprime))
 			return 0;