diff --git a/lib/mining/miner.js b/lib/mining/miner.js
index 3ca66453..2543efc7 100644
--- a/lib/mining/miner.js
+++ b/lib/mining/miner.js
@@ -300,7 +300,9 @@ Miner.prototype._createBlock = co(function* createBlock(tip, address) {
     address: address,
     coinbaseFlags: this.options.coinbaseFlags,
     witness: this.chain.state.hasWitness(),
-    network: this.network
+    network: this.network,
+    weight: this.options.reservedWeight,
+    sigops: this.options.reservedSigops
   });
 
   this.build(attempt);
@@ -465,7 +467,8 @@ Miner.prototype.build = function build(attempt) {
 
   attempt.refresh();
 
-  assert(block.getWeight() <= attempt.weight);
+  assert(block.getWeight() <= attempt.weight,
+    'Block exceeds reserved weight!');
 };
 
 /**
@@ -493,6 +496,8 @@ function MinerOptions(options) {
   this.priorityWeight = policy.PRIORITY_BLOCK_WEIGHT;
   this.minPriority = policy.MIN_BLOCK_PRIORITY;
   this.maxSigops = consensus.MAX_BLOCK_SIGOPS_COST;
+  this.reservedWeight = 4000;
+  this.reservedSigops = 400;
 
   this.fromOptions(options);
 }
@@ -580,6 +585,16 @@ MinerOptions.prototype.fromOptions = function fromOptions(options) {
     this.minPriority = options.minPriority;
   }
 
+  if (options.reservedWeight != null) {
+    assert(util.isNumber(options.reservedWeight));
+    this.reservedWeight = options.reservedWeight;
+  }
+
+  if (options.reservedSigops != null) {
+    assert(util.isNumber(options.reservedSigops));
+    this.reservedSigops = options.reservedSigops;
+  }
+
   return this;
 };
 
diff --git a/lib/mining/minerblock.js b/lib/mining/minerblock.js
index c65431ff..dcc80272 100644
--- a/lib/mining/minerblock.js
+++ b/lib/mining/minerblock.js
@@ -67,8 +67,8 @@ function MinerBlock(options) {
   this.destroyed = false;
   this.committed = false;
 
-  this.sigops = 0;
-  this.weight = 0;
+  this.sigops = options.sigops;
+  this.weight = options.weight;
   this.fees = 0;
   this.items = [];
 
@@ -119,6 +119,8 @@ MinerBlock.prototype._init = function _init() {
   var hash = encoding.ZERO_HASH;
   var block = this.block;
   var cb = this.coinbase;
+  var weight = 0;
+  var sigops = 0;
   var input, output, commit, padding;
 
   assert(this.coinbaseFlags.length <= 20);
@@ -176,16 +178,16 @@ MinerBlock.prototype._init = function _init() {
   block.txs.push(cb);
 
   // Initialize weight.
-  this.weight = block.getWeight();
+  weight = block.getWeight();
 
   // 4 extra bytes for varint tx count.
-  this.weight += 4 * scale;
+  weight += 4 * scale;
 
   // Padding for the CB height (constant size).
   padding = 5 - input.script.code[0].getSize();
   assert(padding >= 0);
 
-  this.weight += padding * scale;
+  weight += padding * scale;
 
   // Reserved size.
   // Without segwit:
@@ -205,14 +207,14 @@ MinerBlock.prototype._init = function _init() {
   //   CB size = 208
   //   Sigops cost = 4
   if (!this.witness) {
-    assert.equal(this.weight, 840);
+    assert.equal(weight, 840);
     assert.equal(block.getBaseSize() + 4 + padding, 210);
     assert.equal(block.getSize() + 4 + padding, 210);
     assert.equal(cb.getWeight() + padding * scale, 500);
     assert.equal(cb.getBaseSize() + padding, 125);
     assert.equal(cb.getSize() + padding, 125);
   } else {
-    assert.equal(this.weight, 1064);
+    assert.equal(weight, 1064);
     assert.equal(block.getBaseSize() + 4 + padding, 257);
     assert.equal(block.getSize() + 4 + padding, 293);
     assert.equal(cb.getWeight() + padding * scale, 724);
@@ -221,7 +223,7 @@ MinerBlock.prototype._init = function _init() {
   }
 
   // Initialize sigops weight.
-  this.sigops = 4;
+  sigops = 4;
 
   // Setup coinbase flags (variable size).
   input.script.set(1, this.coinbaseFlags);
@@ -236,11 +238,17 @@ MinerBlock.prototype._init = function _init() {
 
   // Ensure the variable size
   // stuff didn't break anything.
-  assert(block.getWeight() <= this.weight,
+  assert(block.getWeight() <= weight,
     'Coinbase exceeds reserved size!');
 
-  assert(cb.getSigopsCost(null, this.flags) <= this.sigops,
-    'Coinbase exceeds reserved sigops');
+  assert(cb.getSigopsCost(null, this.flags) <= sigops,
+    'Coinbase exceeds reserved sigops!');
+
+  assert(this.weight >= weight,
+    'Coinbase exceeds reserved size!');
+
+  assert(this.sigops >= sigops,
+    'Coinbase exceeds reserved sigops!');
 };
 
 /**