diff --git a/lib/mining/minerblock.js b/lib/mining/minerblock.js
index 4e4664ea..73ee7f27 100644
--- a/lib/mining/minerblock.js
+++ b/lib/mining/minerblock.js
@@ -11,6 +11,7 @@ var assert = require('assert');
 var util = require('../utils/util');
 var btcutils = require('../btc/utils');
 var co = require('../utils/co');
+var StaticWriter = require('../utils/staticwriter');
 var constants = require('../protocol/constants');
 var Network = require('../protocol/network');
 var BN = require('bn.js');
@@ -54,7 +55,8 @@ function MinerBlock(options) {
   this.target = btcutils.fromCompact(this.bits).toArrayLike(Buffer, 'le', 32);
   this.locktime = options.locktime;
   this.flags = options.flags;
-  this.extraNonce = new BN(0);
+  this.nonce1 = 0;
+  this.nonce2 = 0;
   this.iterations = 0;
   this.coinbaseFlags = options.coinbaseFlags;
   this.witness = options.witness;
@@ -132,20 +134,15 @@ MinerBlock.prototype._init = function _init() {
   // Height (required in v2+ blocks)
   input.script.set(0, new BN(this.height));
 
-  // extraNonce - incremented when
-  // the nonce overflows.
-  input.script.set(1, this.extraNonce);
-
-  // Add a nonce to ensure we don't
-  // collide with a previous coinbase
-  // of ours. This isn't really
-  // necessary nowdays due to bip34
-  // (used above).
-  input.script.set(2, util.nonce());
-
   // Let the world know this little
   // miner succeeded.
-  input.script.set(3, this.coinbaseFlags);
+  input.script.set(1, this.coinbaseFlags);
+
+  input.script.set(2, util.nonce().slice(0, 4));
+
+  // extraNonce - incremented when
+  // the nonce overflows.
+  input.script.set(3, this.extraNonce());
 
   input.script.compile();
 
@@ -219,7 +216,7 @@ MinerBlock.prototype.updateCoinbase = function updateCoinbase() {
   var output = this.coinbase.outputs[0];
 
   // Update extra nonce.
-  input.script.set(1, this.extraNonce);
+  input.script.set(3, this.extraNonce());
   input.script.compile();
 
   // Update reward.
@@ -235,7 +232,12 @@ MinerBlock.prototype.updateNonce = function updateNonce() {
 
   // Overflow the nonce and increment the extraNonce.
   this.block.nonce = 0;
-  this.extraNonce.iaddn(1);
+
+  this.nonce1++;
+  this.nonce1 &= 0xffffffffffff;
+
+  if (this.nonce1 === 0)
+    this.nonce2++;
 
   // We incremented the extraNonce, need to update coinbase.
   this.updateCoinbase();
@@ -263,6 +265,20 @@ MinerBlock.prototype.updateMerkle = function updateMerkle() {
   this.block.merkleRoot = this.block.createMerkleRoot('hex');
 };
 
+/**
+ * Render extraNonce.
+ * @returns {Buffer}
+ */
+
+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);
+  return bw.render();
+};
+
 /**
  * Add a transaction to the block. Rebuilds the merkle tree,
  * updates coinbase and commitment.
@@ -475,6 +491,7 @@ MinerBlock.prototype.commit = function commit(nonce) {
   this.block.nonce = nonce;
   this.block.mutable = false;
   this.coinbase.mutable = false;
+  return this.block;
 };
 
 /**
diff --git a/lib/utils/encoding.js b/lib/utils/encoding.js
index 60d6b4d3..64cc27ad 100644
--- a/lib/utils/encoding.js
+++ b/lib/utils/encoding.js
@@ -851,6 +851,18 @@ encoding.U32 = function U32(num) {
   return data;
 };
 
+/**
+ * Serialize number as a u32be.
+ * @param {Number} num
+ * @returns {Buffer}
+ */
+
+encoding.U32BE = function U32BE(num) {
+  var data = new Buffer(4);
+  data.writeUInt32BE(num, 0, true);
+  return data;
+};
+
 /**
  * Get size of varint-prefixed bytes.
  * @param {Buffer} data