diff --git a/config/c3d2.nix b/config/c3d2.nix
index 8906d849..459fb3dc 100644
--- a/config/c3d2.nix
+++ b/config/c3d2.nix
@@ -3,9 +3,9 @@
 { zentralwerk, hostRegistry, config, options, lib, pkgs, ... }:
 
 let
-  hqPrefix64 = builtins.head (
+  hqPrefix64 = lib.removeSuffix "::" (builtins.head (
     builtins.split "/" zentralwerk.lib.config.site.net.c3d2.subnets6.dn42
-  );
+  ));
 
   # Generate a deterministic IPv6 address for a 64 bit prefix
   # and seed string. Prefix must not contain trailing ':'.