diff --git a/lib/dns/diff.c b/lib/dns/diff.c
index 9ab3ff7cc4..e8dcae9fbc 100644
--- a/lib/dns/diff.c
+++ b/lib/dns/diff.c
@@ -139,19 +139,6 @@ dns_diff_append(dns_diff_t *diff, dns_difftuple_t **tuplep) {
 	*tuplep = NULL;
 }
 
-bool
-dns_diff_is_boundary(const dns_diff_t *diff, dns_name_t *new_name) {
-	REQUIRE(DNS_DIFF_VALID(diff));
-	REQUIRE(DNS_NAME_VALID(new_name));
-
-	if (ISC_LIST_EMPTY(diff->tuples)) {
-		return false;
-	}
-
-	dns_difftuple_t *tail = ISC_LIST_TAIL(diff->tuples);
-	return !dns_name_caseequal(&tail->name, new_name);
-}
-
 size_t
 dns_diff_size(const dns_diff_t *diff) {
 	REQUIRE(DNS_DIFF_VALID(diff));
diff --git a/lib/dns/include/dns/diff.h b/lib/dns/include/dns/diff.h
index 32e81890de..eb9ad1e8c1 100644
--- a/lib/dns/include/dns/diff.h
+++ b/lib/dns/include/dns/diff.h
@@ -187,16 +187,6 @@ dns_diff_append(dns_diff_t *diff, dns_difftuple_t **tuple);
  * \li	The tuple has been freed, or will be freed when the diff is cleared.
  */
 
-bool
-dns_diff_is_boundary(const dns_diff_t *diff, dns_name_t *name);
-/*%<
- * Checks if 'name' is equal, up to case, to the last name of the diff.
- *
- * Requires:
- * \li	'diff' is a valid diff.
- * \li	'name' is a valid dns name.
- */
-
 size_t
 dns_diff_size(const dns_diff_t *diff);
 /*%<
diff --git a/lib/dns/xfrin.c b/lib/dns/xfrin.c
index 8f974c8746..4cd74212bc 100644
--- a/lib/dns/xfrin.c
+++ b/lib/dns/xfrin.c
@@ -324,9 +324,7 @@ axfr_putdata(dns_xfrin_t *xfr, dns_diffop_t op, dns_name_t *name, dns_ttl_t ttl,
 	}
 
 	CHECK(dns_zone_checknames(xfr->zone, name, rdata));
-	if (dns_diff_size(&xfr->diff) > 128 &&
-	    dns_diff_is_boundary(&xfr->diff, name))
-	{
+	if (dns_diff_size(&xfr->diff) > 128) {
 		xfrin_work_t work = (xfrin_work_t){
 			.magic = XFRIN_WORK_MAGIC,
 			.result = ISC_R_UNSET,