diff --git a/krebs/3modules/makefu/default.nix b/krebs/3modules/makefu/default.nix
index b93b34d24..814e6929b 100644
--- a/krebs/3modules/makefu/default.nix
+++ b/krebs/3modules/makefu/default.nix
@@ -548,7 +548,7 @@ TNs2RYfwDy/r6H/hDeB/BSngPouedEVcPwIDAQAB
       nets = {
         retiolum = {
           ip4.addr = "10.243.0.163";
-          ip6.addr = "42:b67b:5752:a730:5f28:d80d:6b37:5bda/128";
+          ip6.addr = "42:b67b:5752:a730:5f28:d80d:6b37:5bda";
           aliases = [
             "senderechner.r"
           ];
diff --git a/krebs/4lib/types.nix b/krebs/4lib/types.nix
index 6396927dd..f46491801 100644
--- a/krebs/4lib/types.nix
+++ b/krebs/4lib/types.nix
@@ -223,7 +223,14 @@ types // rec {
     in x: match IPv4address x != null;
     merge = mergeOneOption;
   };
-  addr6 = str; # TODO
+  addr6 = mkOptionType {
+    name = "IPv6 address";
+    check = let
+      # TODO check IPv6 address harder
+      IPv6address = "[0-9a-f.:]+";
+    in x: match IPv6address x != null;
+    merge = mergeOneOption;
+  };
 
   pgp-pubkey = str;