diff --git a/lib/dns/rdataset.c b/lib/dns/rdataset.c
index ab02d32e09..f70dae9984 100644
--- a/lib/dns/rdataset.c
+++ b/lib/dns/rdataset.c
@@ -337,6 +337,7 @@ towiresorted(dns_rdataset_t *rdataset, const dns_name_t *owner_name,
 	 */
 
 	REQUIRE(DNS_RDATASET_VALID(rdataset));
+	REQUIRE(rdataset->methods != NULL);
 	REQUIRE(countp != NULL);
 	REQUIRE((order == NULL) == (order_arg == NULL));
 	REQUIRE(cctx != NULL && cctx->mctx != NULL);