diff --git a/nix-js/runtime-ts/src/builtins/functional.ts b/nix-js/runtime-ts/src/builtins/functional.ts
index 74e3c93..8ccf7ff 100644
--- a/nix-js/runtime-ts/src/builtins/functional.ts
+++ b/nix-js/runtime-ts/src/builtins/functional.ts
@@ -2,10 +2,11 @@
  * Functional programming builtin functions
  */
 
-import { CatchableError, HAS_CONTEXT, type NixValue } from "../types";
+import { CatchableError, type NixValue } from "../types";
 import { force } from "../thunk";
 import { coerceToString, StringCoercionMode } from "./conversion";
 import { printValue } from "../print";
+import { isAttrs } from "./type-check";
 
 export const seq =
   (e1: NixValue) =>
@@ -17,16 +18,25 @@ export const seq =
 export const deepSeq =
   (e1: NixValue) =>
   (e2: NixValue): NixValue => {
-    const forced = force(e1);
-    if (Array.isArray(forced)) {
-      for (const val of forced) {
-        deepSeq(val);
+    const seen: Set<NixValue> = new Set;
+    const recurse = (e: NixValue) => {
+      if (!seen.has(e)) {
+        seen.add(e);
+      } else {
+        return
       }
-    } else if (typeof forced === "object" && forced !== null && !(HAS_CONTEXT in forced)) {
-      for (const [_, val] of Object.entries(forced)) {
-        deepSeq(val);
+      const forced = force(e);
+      if (Array.isArray(forced)) {
+        for (const val of forced) {
+          recurse(val);
+        }
+      } else if (isAttrs(forced)) {
+        for (const [_, val] of Object.entries(forced)) {
+          recurse(val);
+        }
       }
     }
+    recurse(e1);
     return e2;
   };