diff --git a/pkgs/top-level/config.nix b/pkgs/top-level/config.nix
index ad06227e74f1..e038973e0858 100644
--- a/pkgs/top-level/config.nix
+++ b/pkgs/top-level/config.nix
@@ -128,7 +128,7 @@ let
 in {
 
   freeformType =
-    let t = lib.types.attrsOf lib.types.raw;
+    let t = lib.types.lazyAttrsOf lib.types.raw;
     in t // {
       merge = loc: defs:
         let r = t.merge loc defs;