diff --git a/src/storage.cr b/src/storage.cr
index ed254d1..a604b68 100644
--- a/src/storage.cr
+++ b/src/storage.cr
@@ -341,15 +341,15 @@ class DNSManager::Storage
 		# Same address, no need to change anything.
 		return Response::Success.new if rr.target == address
 
-		# TODO: validate target?
-
 		case rr
 		when Zone::A
+			return Response::Error.new "invalid ipv4" unless Zone.is_ipv4_address_valid? address
 			rr.target = address
 			zone.update_rr rr
 			zones_by_domain.update_or_create zone.domain, zone
 			Response::Success.new
 		when Zone::AAAA
+			return Response::Error.new "invalid ipv6" unless Zone.is_ipv6_address_valid? address
 			rr.target = address
 			zone.update_rr rr
 			update_zone zone