diff --git a/ipv6/mx.cidr b/ipv6/mx.cidr
index 395d3dba..94aac5d3 100644
--- a/ipv6/mx.cidr
+++ b/ipv6/mx.cidr
@@ -69,6 +69,7 @@
 2801:c4:250::/47
 2801:c4:259::/48
 2801:c4:278::/48
+2801:c4:280::/44
 2801:c5::/32
 2801:d0::/32
 2801:f0::/48