diff --git a/lib/redmine/helpers/gantt.rb b/lib/redmine/helpers/gantt.rb
index 9b68f32c2a..416c07afdf 100644
--- a/lib/redmine/helpers/gantt.rb
+++ b/lib/redmine/helpers/gantt.rb
@@ -347,6 +347,7 @@ module Redmine
         if options[:format] == :html
           data_options = {}
           data_options[:collapse_expand] = "issue-#{issue.id}"
+          data_options[:default_top] = "#{options[:top]}px"
           style = "position: absolute;top: #{options[:top]}px; font-size: 0.8em;"
           content =
             view.content_tag(
@@ -780,6 +781,7 @@ module Redmine
               :top_increment => params[:top_increment],
               :obj_id => "#{object.class}-#{object.id}".downcase,
             },
+            :default_top => "#{params[:top]}px",
           }
         end
         if has_children
@@ -835,7 +837,10 @@ module Redmine
       def html_task(params, coords, markers, label, object)
         output = +''
         data_options = {}
-        data_options[:collapse_expand] = "#{object.class}-#{object.id}".downcase if object
+        if object
+          data_options[:collapse_expand] = "#{object.class}-#{object.id}".downcase
+          data_options[:default_top] = "#{params[:top]}px"
+        end
         css = "task " +
           case object
           when Project
diff --git a/public/javascripts/gantt.js b/public/javascripts/gantt.js
index da3b86b7a3..c0735b233a 100644
--- a/public/javascripts/gantt.js
+++ b/public/javascripts/gantt.js
@@ -253,13 +253,16 @@ ganttEntryClick = function(e){
   subject.nextAll('div').each(function(_, element){
     var el = $(element);
     var json = el.data('collapse-expand');
+    var default_top = el.data('default-top');
+    var el_task_bars = $('#gantt_area form > div[data-collapse-expand="' + json.obj_id + '"][data-default-top="' + default_top + '"]');
+    var el_selected_columns = $('td.gantt_selected_column div[data-collapse-expand="' + json.obj_id + '"][data-default-top="' + default_top + '"]');
     if(out_of_hierarchy || parseInt(el.css('left')) <= subject_left){
       out_of_hierarchy = true;
       if(target_shown == null) return false;
 
       var new_top_val = parseInt(el.css('top')) + total_height * (target_shown ? -1 : 1);
       el.css('top', new_top_val);
-      $('#gantt_area form > div[data-collapse-expand="' + json.obj_id + '"], td.gantt_selected_column div[data-collapse-expand="' + json.obj_id + '"]').each(function(_, el){
+      [el_task_bars, el_selected_columns].forEach(function(el){
         $(el).css('top', new_top_val);
       });
       return true;
@@ -272,15 +275,14 @@ ganttEntryClick = function(e){
       total_height = 0;
     }
     if(is_shown == target_shown){
-      $('#gantt_area form > div[data-collapse-expand="' + json.obj_id + '"]').each(function(_, task) {
+      el_task_bars.each(function(_, task) {
         var el_task = $(task);
         if(!is_shown)
           el_task.css('top', target_top + total_height);
         if(!el_task.hasClass('tooltip'))
           el_task.toggle(!is_shown);
       });
-      $('td.gantt_selected_column div[data-collapse-expand="' + json.obj_id + '"]'
-          ).each(function (_, attr) {
+      el_selected_columns.each(function (_, attr) {
         var el_attr = $(attr);
         if (!is_shown)
           el_attr.css('top', target_top + total_height);