diff --git a/lib/miner/miner.js b/lib/miner/miner.js
index bcdecf02..83fd6e1b 100644
--- a/lib/miner/miner.js
+++ b/lib/miner/miner.js
@@ -54,6 +54,7 @@ function Miner(options) {
 
   this.minWeight = 0;
   this.maxWeight = 750000 * constants.WITNESS_SCALE_FACTOR;
+  this.maxSigops = constants.block.MAX_SIGOPS_WEIGHT;
   this.priorityWeight = 50000 * constants.WITNESS_SCALE_FACTOR;
   this.minPriority = constants.tx.FREE_THRESHOLD;
 
@@ -103,6 +104,12 @@ Miner.prototype._initOptions = function _initOptions(options) {
     this.maxWeight = options.maxWeight;
   }
 
+  if (options.maxSigops != null) {
+    assert(utils.isNumber(options.maxSigops));
+    assert(options.maxSigops <= constants.block.MAX_SIGOPS_WEIGHT);
+    this.maxSigops = options.maxSigops;
+  }
+
   if (options.priorityWeight != null) {
     assert(utils.isNumber(options.priorityWeight));
     this.priorityWeight = options.priorityWeight;
@@ -332,7 +339,7 @@ Miner.prototype.createBlock = co(function* createBlock(tip, address) {
     network: this.network
   });
 
-  this.fill(attempt);
+  this.build(attempt);
 
   return attempt;
 });
@@ -387,10 +394,11 @@ Miner.prototype.getAddress = function getAddress() {
 
 /**
  * Get mempool entries, sort by dependency order.
+ * Prioritize by priority and fee rates.
  * @returns {MempoolEntry[]}
  */
 
-Miner.prototype.fill = function fill(attempt) {
+Miner.prototype.build = function build(attempt) {
   var depMap = {};
   var block = attempt.block;
   var queue = new Queue(cmpPriority);
@@ -456,11 +464,13 @@ Miner.prototype.fill = function fill(attempt) {
 
     sigops += tx.getSigopsWeight(attempt.flags);
 
-    if (sigops > constants.block.MAX_SIGOPS_WEIGHT)
+    if (sigops > this.maxSigops)
       continue;
 
     if (priority) {
       if (weight > this.priorityWeight || item.priority < this.minPriority) {
+        // Todo: Compare descendant rate with
+        // cumulative fees and cumulative vsize.
         queue.cmp = cmpRate;
         priority = false;
         queue.push(item);