diff --git a/nix-js/runtime-ts/src/builtins/attrs.ts b/nix-js/runtime-ts/src/builtins/attrs.ts
index bfb0784..88fe3fd 100644
--- a/nix-js/runtime-ts/src/builtins/attrs.ts
+++ b/nix-js/runtime-ts/src/builtins/attrs.ts
@@ -4,6 +4,7 @@
 
 import type { NixValue, NixAttrs, NixList } from "../types";
 import { forceAttrs, forceString, forceFunction, forceList } from "../type-assert";
+import { createThunk } from "../thunk";
 
 export const attrNames = (set: NixValue): string[] => Object.keys(forceAttrs(set)).sort();
 
@@ -22,17 +23,13 @@ export const hasAttr =
 export const mapAttrs =
   (f: NixValue) =>
   (attrs: NixValue): NixAttrs => {
-    const forced_attrs = forceAttrs(attrs);
-    const forced_f = forceFunction(f);
-    const new_attrs: NixAttrs = {};
-    for (const key in forced_attrs) {
-      Object.defineProperty(new_attrs, key, {
-        get: () => forceFunction(forced_f(key))(forced_attrs[key]),
-        enumerable: true,
-        configurable: true,
-      });
+    const forcedAttrs = forceAttrs(attrs);
+    const forcedF = forceFunction(f);
+    const newAttrs: NixAttrs = {};
+    for (const key in forcedAttrs) {
+      newAttrs[key] = createThunk(() => forceFunction(forcedF(key))(forcedAttrs[key]));
     }
-    return new_attrs;
+    return newAttrs;
   };
 
 export const removeAttrs =
diff --git a/nix-js/runtime-ts/src/operators.ts b/nix-js/runtime-ts/src/operators.ts
index 5d05522..fa06582 100644
--- a/nix-js/runtime-ts/src/operators.ts
+++ b/nix-js/runtime-ts/src/operators.ts
@@ -250,27 +250,5 @@ export const op = {
     return Array.prototype.concat.call(forceList(a), forceList(b));
   },
 
-  update: (a: NixValue, b: NixValue): NixAttrs => {
-    const forcedA = forceAttrs(a);
-    const forcedB = forceAttrs(b);
-    const newAttrs: NixAttrs = {};
-
-    for (const key in forcedA) {
-      Object.defineProperty(newAttrs, key, {
-        get: () => force(forcedA[key]),
-        enumerable: true,
-        configurable: true,
-      });
-    }
-
-    for (const key in forcedB) {
-      Object.defineProperty(newAttrs, key, {
-        get: () => force(forcedB[key]),
-        enumerable: true,
-        configurable: true,
-      });
-    }
-
-    return newAttrs;
-  },
+  update: (a: NixValue, b: NixValue): NixAttrs => ({ ...forceAttrs(a), ...forceAttrs(b) }),
 };