diff --git a/db/ptr.sql b/db/ptr.sql
index c7d022c7..0952aec8 100644
--- a/db/ptr.sql
+++ b/db/ptr.sql
@@ -1,36 +1,20 @@
+-- Reverse DNS name of an address. Plain SQL (no STRICT, no sub-SELECT, only
+-- immutable functions) so Postgres inlines it into the calling query; it
+-- expands the address from the inet_send() wire bytes (4 header bytes, then
+-- the address), so the netmask is ignored. Kept in sync with
+-- serveradmin_extras/serveradmin_powerdns/migrations/0006_ptr_function.py.
 create or replace function public.ptr(intern_ip inet) returns text
-immutable strict language plpgsql as $$
-declare
-    ip_part text;
-    ip_text text;
-    ip_arr text[];
-    ip_filled boolean;
-begin
-    if family(intern_ip) = 4 then
-        return (
-            select string_agg(part, '.'  order by ord desc) || '.in-addr.arpa'
-            from regexp_split_to_table(host(intern_ip), '\.') with ordinality as s(part, ord)
-        );
+language sql immutable parallel safe as $$
+select case family(intern_ip)
+    when 4 then
+        get_byte(inet_send(intern_ip), 7)::text || '.' ||
+        get_byte(inet_send(intern_ip), 6)::text || '.' ||
+        get_byte(inet_send(intern_ip), 5)::text || '.' ||
+        get_byte(inet_send(intern_ip), 4)::text || '.in-addr.arpa'
     else
-        ip_text := '';
-        ip_arr := regexp_split_to_array(host(intern_ip), ':');
-        ip_filled = false;
-
-        foreach ip_part in array ip_arr loop
-            if length(ip_part) = 0 and not ip_filled then
-                ip_text := ip_text || repeat('0', 32 - (array_length(ip_arr, 1) - 1) * 4);
-                ip_filled = true;
-            else
-                ip_text := ip_text || lpad(ip_part, 4, '0');
-            end if;
-        end loop;
-
-        return (
-            select string_agg(part[1], '.' order by ord desc) || '.ip6.arpa'
-            from regexp_matches(ip_text, '.', 'g') with ordinality as s(part, ord)
-        );
-    end if;
-end;
+        regexp_replace(reverse(encode(substring(inet_send(intern_ip) from 5), 'hex')), '(.)', '\1.', 'g')
+        || 'ip6.arpa'
+end
 $$;
 
 create index concurrently server_ptr_idx on public.server(public.ptr(intern_ip) text_pattern_ops);