diff --git a/ops/nixos/lib/blade-router.nix b/ops/nixos/lib/blade-router.nix
index 2d481ffc03..a88b25ec06 100644
--- a/ops/nixos/lib/blade-router.nix
+++ b/ops/nixos/lib/blade-router.nix
@@ -65,7 +65,7 @@ in {
     };
 
     addresses.br-public-radvd-prefix = {
-      addr = mkOption { type = types.str; default = "2a09:a441:ffff:ffff::"; };
+      addr = mkOption { type = types.str; default = "2a09:a441:0:ffff::"; };
       prefixLength = mkOption { type = types.int; default = 64; };
     };