diff --git a/modules/system/default.nix b/modules/system/default.nix
index 3144695..733a73a 100644
--- a/modules/system/default.nix
+++ b/modules/system/default.nix
@@ -20,7 +20,7 @@ in
 
     system.build = mkOption {
       internal = true;
-      type = types.attrsOf types.unspecified;
+      type = types.lazyAttrsOf types.unspecified;
       default = {};
       description = ''
         Attribute set of derivation used to setup the system.