diff --git a/lib/mempool/fees.js b/lib/mempool/fees.js
index bc3436ab..ef1482ce 100644
--- a/lib/mempool/fees.js
+++ b/lib/mempool/fees.js
@@ -656,13 +656,13 @@ PolicyEstimator.prototype.processBlock = function processBlock(height, entries,
 
 /**
  * Estimate a fee rate.
- * @param {Number} target - Confirmation target.
+ * @param {Number} [target=1] - Confirmation target.
  * @param {Boolean} [smart=true] - Smart estimation.
  * @returns {Rate}
  */
 
 PolicyEstimator.prototype.estimateFee = function estimateFee(target, smart) {
-  var rate, minPoolFee;
+  var rate;
 
   if (!target)
     target = 1;
@@ -670,8 +670,9 @@ PolicyEstimator.prototype.estimateFee = function estimateFee(target, smart) {
   if (smart == null)
     smart = true;
 
-  if (!(target > 0) || target > this.feeStats.maxConfirms)
-    return 0;
+  assert(utils.isUInt32(target), 'Target must be a number.');
+  assert(target <= this.feeStats.maxConfirms,
+    'Too many confirmations for estimate.');
 
   if (!smart) {
     rate = this.feeStats.estimateMedian(
@@ -693,9 +694,8 @@ PolicyEstimator.prototype.estimateFee = function estimateFee(target, smart) {
 
   target -= 1;
 
-  minPoolFee = this.network.minRelay;
-  if (minPoolFee > 0 && minPoolFee > rate)
-    return minPoolFee;
+  if (rate < this.network.feeRate)
+    return this.network.feeRate;
 
   if (rate < 0)
     return 0;
@@ -705,13 +705,13 @@ PolicyEstimator.prototype.estimateFee = function estimateFee(target, smart) {
 
 /**
  * Estimate a priority.
- * @param {Number} target - Confirmation target.
+ * @param {Number} [target=1] - Confirmation target.
  * @param {Boolean} [smart=true] - Smart estimation.
  * @returns {Number}
  */
 
 PolicyEstimator.prototype.estimatePriority = function estimatePriority(target, smart) {
-  var minPoolFee, priority;
+  var priority;
 
   if (!target)
     target = 1;
@@ -719,8 +719,9 @@ PolicyEstimator.prototype.estimatePriority = function estimatePriority(target, s
   if (smart == null)
     smart = true;
 
-  if (!(target > 0) || target > this.priStats.maxConfirms)
-    return 0;
+  assert(utils.isUInt32(target), 'Target must be a number.');
+  assert(target <= this.priStats.maxConfirms,
+    'Too many confirmations for estimate.');
 
   if (!smart) {
     priority = this.priStats.estimateMedian(
@@ -729,9 +730,8 @@ PolicyEstimator.prototype.estimatePriority = function estimatePriority(target, s
     return Math.floor(priority);
   }
 
-  minPoolFee = this.network.minRelay;
-  if (minPoolFee > 0)
-    return INF_PRIORITY;
+  // TODO: Add check for mempool limiting txs.
+  // Should return INF_PRIORITY.
 
   priority = -1;
   while (priority < 0 && target <= this.priStats.maxConfirms) {