diff --git a/ipv6/us.cidr b/ipv6/us.cidr
index cc0701823..9d5f0d2f6 100644
--- a/ipv6/us.cidr
+++ b/ipv6/us.cidr
@@ -1026,6 +1026,7 @@
 2602:81b:5000::/44
 2602:81b:6000::/44
 2602:81b:7000::/44
+2602:f666::/40
 2602:f667::/36
 2602:f668::/36
 2602:f669::/40