diff --git a/modules/system/backups.nix b/modules/system/backups.nix
index 6bf8926..3a9e945 100644
--- a/modules/system/backups.nix
+++ b/modules/system/backups.nix
@@ -24,7 +24,7 @@ in
   options.modules.system.backups = {
     enable = lib.mkEnableOption "enables backups with borg";
     baks = lib.mkOption {
-      type = lib.types.attrsOf ( lib.types.attrsOf lib.types.any );
+      type = lib.types.attrsOf ( lib.types.attrsOf (lib.types.listOf lib.types.null) );
       default = {};
       description = "backup jobs, nested attribute sets should be <bak_name> = paths [<list_of_paths>]";
     };