diff --git a/packages/rln/src/utils/bytes.ts b/packages/rln/src/utils/bytes.ts
index 6e4f022055..cb157b114b 100644
--- a/packages/rln/src/utils/bytes.ts
+++ b/packages/rln/src/utils/bytes.ts
@@ -61,9 +61,13 @@ export function writeUIntLE(
  * @param array: Uint8Array
  * @returns BigInt
  */
-export function buildBigIntFromUint8Array(array: Uint8Array): bigint {
+export function buildBigIntFromUint8Array(
+  array: Uint8Array,
+  byteOffset: number = 0
+): bigint {
+  // Use all bytes from byteOffset to the end, big-endian
   let hex = "";
-  for (let i = array.length - 1; i >= 0; i--) {
+  for (let i = byteOffset; i < array.length; i++) {
     hex += array[i].toString(16).padStart(2, "0");
   }
   return BigInt("0x" + hex);