diff --git a/options.nix b/options.nix
index 9466eb4..9ea8361 100644
--- a/options.nix
+++ b/options.nix
@@ -164,6 +164,11 @@ in
                  || (!currentMachine.profiles.isServer);
        message = "A graphical environment is not required for a server.";
      }
+     {
+       /*  At least one (authorité or resolveur) */
+       assertion = flags.dns_autorite || flags.dns_resolveur;
+       message = "DNS service is disabled. You must enable a dns recursor or autoritative.";
+     }
      {
        /*  authorité xor resolveur */
        assertion = (flags.dns_autorite && ! flags.dns_resolveur)