diff --git a/nix/lib/config/legacy.nix b/nix/lib/config/legacy.nix
index 45d7d44..2690ff8 100644
--- a/nix/lib/config/legacy.nix
+++ b/nix/lib/config/legacy.nix
@@ -74,7 +74,7 @@ in
         data = "1 1 6789 ${host}";
       }) cephMonServers ++
       lib.lists.imap0 (i: host: {
-        name = "mon${i}";
+        name = "mon${toString i}";
         type = "CNAME";
         data = "${host}";
       }) cephMonServers;