diff --git a/lib/miner/miner.js b/lib/miner/miner.js
index dfda84bf..01060435 100644
--- a/lib/miner/miner.js
+++ b/lib/miner/miner.js
@@ -207,23 +207,23 @@ Miner.prototype.stop = co(function* stop() {
  * Wait for `done` event.
  */
 
-Miner.prototype._onDone = co(function* _onDone() {
+Miner.prototype._onDone = function _onDone() {
   var self = this;
   return new Promise(function(resolve, reject) {
     self.once('done', resolve);
   });
-});
+};
 
 /**
  * Wait for `stop` event.
  */
 
-Miner.prototype._onStop = co(function* _onStop() {
+Miner.prototype._onStop = function _onStop() {
   var self = this;
   return new Promise(function(resolve, reject) {
     self.once('stop', resolve);
   });
-});
+};
 
 /**
  * Create a block "attempt".