diff --git a/app/helpers/issues_helper.rb b/app/helpers/issues_helper.rb
index 81b23acb37..056185c611 100644
--- a/app/helpers/issues_helper.rb
+++ b/app/helpers/issues_helper.rb
@@ -41,7 +41,8 @@ module IssuesHelper
             !issue.is_descendant_of?(ancestors.last)
         ancestors.pop
       end
-      yield issue, ancestors.size, group_name, group_count, group_totals
+      level = (query.grouped? && query.group_by_column.name == :parent) ? 0 : ancestors.size
+      yield issue, level, group_name, group_count, group_totals
       ancestors << issue unless issue.leaf?
     end
   end
diff --git a/app/models/issue_query.rb b/app/models/issue_query.rb
index efd0ad0f1d..54db6a3bf7 100644
--- a/app/models/issue_query.rb
+++ b/app/models/issue_query.rb
@@ -28,6 +28,7 @@ class IssueQuery < Query
     QueryColumn.new(:tracker, :sortable => "#{Tracker.table_name}.position", :groupable => true),
     QueryColumn.new(:parent,
                     :sortable => ["#{Issue.table_name}.root_id", "#{Issue.table_name}.lft ASC"],
+                    :groupable => "#{Issue.table_name}.parent_id",
                     :default_order => 'desc', :caption => :field_parent_issue),
     QueryAssociationColumn.new(:parent, :subject, :caption => :field_parent_issue_subject),
     QueryColumn.new(:status, :sortable => "#{IssueStatus.table_name}.position", :groupable => true),
diff --git a/app/models/query.rb b/app/models/query.rb
index c49e4f4d11..5c74516326 100644
--- a/app/models/query.rb
+++ b/app/models/query.rb
@@ -18,8 +18,8 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 class QueryColumn
-  attr_accessor :name, :totalable, :default_order
-  attr_writer   :sortable, :groupable
+  attr_accessor :name, :totalable, :default_order, :groupable
+  attr_writer   :sortable
 
   include Redmine::I18n
 
@@ -906,6 +906,9 @@ class Query < ActiveRecord::Base
       if column.is_a?(TimestampQueryColumn)
         column_sortable = Redmine::Database.timestamp_to_date(column.sortable, User.current.time_zone)
       end
+      if column.name == :parent
+        column_sortable = Array(column.groupable)
+      end
       Array(column_sortable).map {|s| Arel.sql("#{s} #{order}")}
     end
   end
diff --git a/test/unit/query_test.rb b/test/unit/query_test.rb
index ccf30f4773..64ce1991f5 100644
--- a/test/unit/query_test.rb
+++ b/test/unit/query_test.rb
@@ -1761,6 +1761,19 @@ class QueryTest < ActiveSupport::TestCase
     assert_nil q.group_by_statement
   end
 
+  def test_grouped_with_parent_task_should_sort_by_parent_id
+    Issue.delete_all
+    first, second, third  = Issue.generate!, Issue.generate!, Issue.generate!
+    Issue.generate!(:parent_id => second.id)
+    Issue.generate!(:parent_id => third.id)
+    Issue.generate!(:parent_id => first.id)
+
+    q = IssueQuery.new(:group_by => 'parent')
+    assert_equal :parent, q.group_by_column.name
+    assert_equal ["#{Issue.table_name}.parent_id DESC"], q.group_by_sort_order
+    assert_equal [third.id, second.id, first.id, nil, nil, nil], q.issues.pluck(:parent_id)
+  end
+
   def test_sortable_columns_should_sort_assignees_according_to_user_format_setting
     with_settings :user_format => 'lastname_comma_firstname' do
       q = IssueQuery.new