diff --git a/lib/utils/async.js b/lib/utils/async.js
index b7967f30..0fd09abb 100644
--- a/lib/utils/async.js
+++ b/lib/utils/async.js
@@ -38,20 +38,6 @@ utils.inherits(AsyncObject, EventEmitter);
  * @returns {Promise}
  */
 
-AsyncObject.prototype._onOpen = function _onOpen() {
-  var self = this;
-  return new Promise(function(resolve, reject) {
-    return self.once('open', resolve);
-  });
-};
-
-AsyncObject.prototype._onClose = function _onClose() {
-  var self = this;
-  return new Promise(function(resolve, reject) {
-    return self.once('close', resolve);
-  });
-};
-
 AsyncObject.prototype.open = co(function* open() {
   var err, unlock;
 
@@ -188,6 +174,32 @@ AsyncObject.prototype._close = function _close(callback) {
   throw new Error('Abstract method.');
 };
 
+/**
+ * Wait for open event.
+ * @private
+ * @returns {Promise}
+ */
+
+AsyncObject.prototype._onOpen = function _onOpen() {
+  var self = this;
+  return new Promise(function(resolve, reject) {
+    return self.once('open', resolve);
+  });
+};
+
+/**
+ * Wait for close event.
+ * @private
+ * @returns {Promise}
+ */
+
+AsyncObject.prototype._onClose = function _onClose() {
+  var self = this;
+  return new Promise(function(resolve, reject) {
+    return self.once('close', resolve);
+  });
+};
+
 /*
  * Expose
  */