diff --git a/lib/utils/encoding.js b/lib/utils/encoding.js
index 7b6d70ad..120464cf 100644
--- a/lib/utils/encoding.js
+++ b/lib/utils/encoding.js
@@ -574,7 +574,7 @@ encoding.sizeVarint = function sizeVarint(num) {
  */
 
 encoding.readVarintBN = function readVarintBN(data, off) {
-  var value, size;
+  var result, value, size;
 
   assert(off < data.length);
 
@@ -586,7 +586,9 @@ encoding.readVarintBN = function readVarintBN(data, off) {
       assert(value.bitLength() > 32);
       return new Varint(size, value);
     default:
-      return encoding.readVarint(data, off);
+      result = encoding.readVarint(data, off);
+      result.value = new BN(result.value);
+      return result;
   }
 };
 
@@ -600,9 +602,9 @@ encoding.readVarintBN = function readVarintBN(data, off) {
 
 encoding.writeVarintBN = function writeVarintBN(dst, num, off) {
   if (num.bitLength() > 32) {
-    dst[off] = 0xff;
-    encoding.writeU64BN(dst, num, off + 1);
-    return off + 9;
+    dst[off++] = 0xff;
+    off = encoding.writeU64BN(dst, num, off);
+    return off;
   }
 
   return encoding.writeVarint(dst, num.toNumber(), off);