diff --git a/app/models/activity_feed_observer.rb b/app/models/activity_feed_observer.rb
index 0cc2c2737..95f3fe3d5 100644
--- a/app/models/activity_feed_observer.rb
+++ b/app/models/activity_feed_observer.rb
@@ -22,7 +22,7 @@ class ActivityFeedObserver < ActiveRecord::Observer
         )
       end
 
-      if record.user_id_was != record.user_id
+      if record.user_id_changed?
         UserMailer.delay.issue_assign_notification(record, record.user) if record.user.notifier.issue_assign && record.user.notifier.can_notify
         ActivityFeed.create(
           :user => record.user,
@@ -106,7 +106,7 @@ class ActivityFeedObserver < ActiveRecord::Observer
   def after_update(record)
     case record.class.to_s
     when 'Issue'
-      if record.user_id_was != record.user_id
+      if record.user_id && record.user_id_changed?
         UserMailer.delay.issue_assign_notification(record, record.user) if record.user.notifier.issue_assign && record.user.notifier.can_notify
         ActivityFeed.create(
           :user => record.user,
diff --git a/app/models/issue.rb b/app/models/issue.rb
index a3bd0f2e1..1a9ce3fad 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -80,7 +80,7 @@ class Issue < ActiveRecord::Base
   end
 
   def subscribe_issue_assigned_user
-    if self.user_id_was != self.user_id
+    if self.user_id && self.user_id_changed?
       self.subscribes.where(:user_id => self.user_id_was).first.destroy unless self.user_id_was.blank?
       if self.user.notifier.issue_assign && !self.subscribes.exists?(:user_id => self.user_id)
         self.subscribes.create(:user_id => self.user_id)
diff --git a/app/views/issues/_manage_sidebar.html.haml b/app/views/issues/_manage_sidebar.html.haml
index bd70ac04c..6cbb2cf42 100644
--- a/app/views/issues/_manage_sidebar.html.haml
+++ b/app/views/issues/_manage_sidebar.html.haml
@@ -14,6 +14,7 @@
     - if @issue.persisted?
       -if can_manage
         =form_for :issue, :url => [@project, @issue], :method => :put, :html => { :class => 'edit_executor issue'} do |f|
+          =hidden_field_tag "user-default_executor", nil, :name => 'issue[user_id]'
           .current_executor
             - if @issue.user
               #user-0.people.nopointer