diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 748a3d06..92841158 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -180,11 +180,9 @@ utils.writeU64 = function writeU64(dst, num, off) {
   if (!off)
     off = 0;
 
-  var n = new bn(num);
-  var left = n.shrn(32);
-  //var right = n.andln(0xffffffff);
-  var right = ((n.words[1] & 0xff) << 24) | n.words[0];
-  if (right < 0) right += 0x100000000;
+  var num = new bn(num);
+  var left = +num.shrn(32).toString(10);
+  var right = +num.maskn(32).toString(10);
 
   dst[off] = right & 0xff;
   dst[off + 1] = (right >>> 8) & 0xff;
@@ -221,11 +219,9 @@ utils.writeU64BE = function writeU64BE(dst, num, off) {
   if (!off)
     off = 0;
 
-  var n = new bn(num);
-  var left = n.shrn(32);
-  //var right = n.andln(0xffffffff);
-  var right = ((n.words[1] & 0xff) << 24) | n.words[0];
-  if (right < 0) right += 0x100000000;
+  var num = new bn(num);
+  var left = +num.shrn(32).toString(10);
+  var right = +num.maskn(32).toString(10);
 
   dst[off] = (left >>> 24) & 0xff;
   dst[off + 1] = (left >>> 16) & 0xff;