diff --git a/nixos/modules/services/networking/kresd.nix b/nixos/modules/services/networking/kresd.nix
index d295e40f3922..3dbd5203094c 100644
--- a/nixos/modules/services/networking/kresd.nix
+++ b/nixos/modules/services/networking/kresd.nix
@@ -65,6 +65,7 @@ in {
       default = "";
       description = ''
         Extra lines to be added verbatim to the generated configuration file.
+        See upstream documentation <https://www.knot-resolver.cz/documentation/stable/config-overview.html> for more details.
       '';
     };
     listenPlain = mkOption {