diff --git a/lib/mining/cpuminer.js b/lib/mining/cpuminer.js
index a869f0d6..f36f42f6 100644
--- a/lib/mining/cpuminer.js
+++ b/lib/mining/cpuminer.js
@@ -528,13 +528,14 @@ CPUJob.prototype.destroy = function destroy() {
 };
 
 /**
- * Calculate number of hashes.
+ * Calculate number of hashes computed.
  * @param {Number} nonce
  * @returns {Number}
  */
 
 CPUJob.prototype.getHashes = function getHashes(nonce) {
-  return this.nonce1 * 0x100000000 + this.nonce2 + nonce;
+  var extra = this.nonce1 * 0x100000000 + this.nonce2;
+  return extra * 0xffffffff + nonce;
 };
 
 /**
@@ -545,7 +546,8 @@ CPUJob.prototype.getHashes = function getHashes(nonce) {
 
 CPUJob.prototype.getRate = function getRate(nonce) {
   var hashes = this.getHashes(nonce);
-  return Math.floor(hashes / (util.now() - this.start));
+  var seconds = util.now() - this.start;
+  return Math.floor(hashes / seconds);
 };
 
 /**