diff --git a/nix-js/runtime-ts/src/conversion.ts b/nix-js/runtime-ts/src/conversion.ts
index a83a429..e00b280 100644
--- a/nix-js/runtime-ts/src/conversion.ts
+++ b/nix-js/runtime-ts/src/conversion.ts
@@ -1,6 +1,7 @@
 import { HAS_CONTEXT, NixStringContext } from "./string-context";
 import { force } from "./thunk";
 import type { NixValue } from "./types";
+import { isStringWithContext } from "./types";
 
 export const nixValueToJson = (
   value: NixValue,
@@ -35,7 +36,6 @@ export const nixValueToJson = (
     if (seen.has(v)) {
       throw new Error("derivation: circular reference detected in __structuredAttrs");
     }
-    // FIXME: tryAttrsToString
     seen.add(v);
   }
 
@@ -44,9 +44,31 @@ export const nixValueToJson = (
   }
 
   if (typeof v === "object") {
+    if ("__toString" in v && typeof force(v.__toString) === "function") {
+      const toStringMethod = force(v.__toString) as (self: typeof v) => NixValue;
+      const result = force(toStringMethod(v));
+      if (typeof result === "string") {
+        return result;
+      }
+      if (isStringWithContext(result)) {
+        if (outContext) {
+          for (const elem of result.context) {
+            outContext.add(elem);
+          }
+        }
+        return result.value;
+      }
+      return nixValueToJson(result, seen, outContext);
+    }
+
+    if ("outPath" in v) {
+      return nixValueToJson(v.outPath, seen, outContext);
+    }
+
     const result: Record<string, any> = {};
-    for (const [key, val] of Object.entries(v)) {
-      result[key] = nixValueToJson(val, seen, outContext);
+    const keys = Object.keys(v).sort();
+    for (const key of keys) {
+      result[key] = nixValueToJson((v as Record<string, NixValue>)[key], seen, outContext);
     }
     return result;
   }