diff --git a/light-zk.js/src/utils.ts b/light-zk.js/src/utils.ts
index dfe4d9ff71..bc9eb315e1 100644
--- a/light-zk.js/src/utils.ts
+++ b/light-zk.js/src/utils.ts
@@ -182,7 +182,7 @@ export const fetchNullifierAccountInfo = async (
 ) => {
   const nullifierPubkey = PublicKey.findProgramAddressSync(
     [
-      Buffer.from(new anchor.BN(nullifier.toString()).toArray()),
+      new anchor.BN(nullifier.toString()).toBuffer("be", 32),
       anchor.utils.bytes.utf8.encode("nf"),
     ],
     merkleTreeProgramId,