diff --git a/lib/mining/minerblock.js b/lib/mining/minerblock.js
index 670b8861..222b9e70 100644
--- a/lib/mining/minerblock.js
+++ b/lib/mining/minerblock.js
@@ -232,8 +232,8 @@ MinerBlock.prototype.updateNonce = function updateNonce() {
   this.block.nonce = 0;
   this.nonce1++;
 
-  // Wrap at 6 bytes.
-  if (this.nonce1 === 0xffffffffffff) {
+  // Wrap at 4 bytes.
+  if (this.nonce1 === 0xffffffff) {
     this.nonce1 = 0;
     this.nonce2++;
   }
@@ -270,11 +270,9 @@ MinerBlock.prototype.updateMerkle = function updateMerkle() {
  */
 
 MinerBlock.prototype.extraNonce = function extraNonce() {
-  var bw = new StaticWriter(12);
-  bw.writeU32BE(this.nonce1 / 0x10000 | 0);
-  bw.writeU16BE(this.nonce1 & 0xffff);
-  bw.writeU32BE(this.nonce2 / 0x10000 | 0);
-  bw.writeU16BE(this.nonce2 & 0xffff);
+  var bw = new StaticWriter(8);
+  bw.writeU32BE(this.nonce1);
+  bw.writeU32BE(this.nonce2);
   return bw.render();
 };