diff --git a/ipv6/in.cidr b/ipv6/in.cidr
index 2f486670d..a7275ccc5 100644
--- a/ipv6/in.cidr
+++ b/ipv6/in.cidr
@@ -1299,6 +1299,7 @@
 2001:df6:140::/48
 2001:df6:340::/48
 2001:df6:5c0::/48
+2001:df6:640::/48
 2001:df6:980::/48
 2001:df6:b80::/48
 2001:df6:c80::/48