diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index fc718da3..5de833ce 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -188,6 +188,10 @@ utils.writeU64 = function writeU64(dst, num, off) {
     dst[off++] = ch;
   });
 
+  var i = num.length;
+  while (i--)
+    dst[off++] = num[i];
+
   return 8;
 };
 
@@ -217,9 +221,8 @@ utils.writeU64BE = function writeU64BE(dst, num, off) {
   while (num.length < 8)
     num.unshift(0);
 
-  num.forEach(function(ch) {
-    dst[off++] = ch;
-  });
+  for (var i = 0; i < num.length; i++)
+    dst[off++] = num[i];
 
   return 8;
 };