diff --git a/nixos/modules/system/activation/top-level.nix b/nixos/modules/system/activation/top-level.nix
index 501998fa399e..42e6dd689f93 100644
--- a/nixos/modules/system/activation/top-level.nix
+++ b/nixos/modules/system/activation/top-level.nix
@@ -148,7 +148,7 @@ in
     system.build = mkOption {
       internal = true;
       default = {};
-      type = types.attrs;
+      type = types.lazyAttrsOf types.unspecified;
       description = ''
         Attribute set of derivations used to setup the system.
       '';