diff --git a/hierarchical_select.module b/hierarchical_select.module
index 120eedb..f3edd7d 100644
--- a/hierarchical_select.module
+++ b/hierarchical_select.module
@@ -25,7 +25,7 @@ function hierarchical_select_menu() {
     'theme callback'    => 'ajax_base_page_theme',
     'type'              => MENU_CALLBACK,
   );
-  
+
   $items['admin/config/content/hierarchical_select'] = array(
     'title'            => 'Hierarchical Select',
     'description'      => 'Configure site-wide settings for the Hierarchical Select form element.',
@@ -360,7 +360,7 @@ function _hs_process_attach_css_js($element, $hsid, &$form_state, $complete_form
   $element['#attached']['library'][] = array('system', 'drupal.ajax');
   $element['#attached']['library'][] = array('system', 'jquery.form');
   $element['#attached']['library'][] = array('system', 'effects');
-  $element['#attached']['library'][] = array('system', 'effects.drop');    
+  $element['#attached']['library'][] = array('system', 'effects.drop');
   $element['#attached']['css'][] = drupal_get_path('module', 'hierarchical_select') . '/hierarchical_select.css';
   $element['#attached']['js'][] = drupal_get_path('module', 'hierarchical_select') . '/hierarchical_select.js';
   if (variable_get('hierarchical_select_js_cache_system', 0) == 1) {
@@ -470,7 +470,7 @@ function _hs_process_developer_mode_log_selections($config, $hs_selection, $db_s
   }
 }
 
-function _hs_process_developer_mode_log_hierarchy_and_dropbox($config, $hierarchy, $dropbox) {  
+function _hs_process_developer_mode_log_hierarchy_and_dropbox($config, $hierarchy, $dropbox) {
   if (HS_DEVELOPER_MODE) {
     _hierarchical_select_log('Generated hierarchy in ' . $hierarchy->build_time['total'] . ' ms:');
     _hierarchical_select_log($hierarchy);
@@ -648,7 +648,7 @@ function _hs_process_render_dropbox($element, $hsid, $creating_new_item, $dropbo
         '#attributes'              => array('class' => array('add-to-dropbox')),
         '#limit_validation_errors' => array($element['#parents']),
         '#validate'                => array(),
-        '#submit'                  => array('hierarchical_select_ajax_update_submit'),        
+        '#submit'                  => array('hierarchical_select_ajax_update_submit'),
       );
     }
 
@@ -662,7 +662,7 @@ function _hs_process_render_dropbox($element, $hsid, $creating_new_item, $dropbo
 
         // Disable all child form elements of $element['hierarchical_select].
         // _hierarchical_select_mark_as_disabled($element['hierarchical_select']);
-        
+
         // TODO: make the above work again. Currently, we're just disabling
         // the "Add" button. #disabled can't be used for the same reasons as
         // described in _hierarchical_select_mark_as_disabled().
@@ -675,7 +675,7 @@ function _hs_process_render_dropbox($element, $hsid, $creating_new_item, $dropbo
     if (isset($dropbox->lineages_selections)) {
       $form_state['storage']['hs'][$hsid]['dropbox_lineages_selections'] = $dropbox->lineages_selections;
     }
-    
+
     // Add the dropbox-as-a-table that will be visible to the user.
     $element['dropbox']['visible'] = _hs_process_render_db_table($hsid, $dropbox);
   }
@@ -1006,7 +1006,7 @@ function _hierarchical_select_process_get_hs_selection($element) {
  *   An array (bag) containing the ids of the selected items in the
  *   dropbox.
  */
-function _hierarchical_select_process_get_db_selection($element, $hsid, $form_state) {
+function _hierarchical_select_process_get_db_selection($element, $hsid, &$form_state) {
   $db_selection = array();
 
   if (!empty($form_state['storage']['hs'][$hsid]['dropbox_lineages_selections'])) {
@@ -1017,6 +1017,11 @@ function _hierarchical_select_process_get_db_selection($element, $hsid, $form_st
         if ($remove_value['remove'] === '1') {
           // $x is of the form "lineage-<number>". Extract the number.
           $remove_from_db_selection[] = substr($x, 8);
+          // By removing the input (POST) reference to the remove checkbox,
+          // we make sure that on a form rebuilt, the same remove checkbox,
+          // which is accessed by index, is not set, preventing a double removal
+          // @see https://www.drupal.org/node/1566878#comment-9226261
+          unset($form_state['input']['parent']['dropbox']['visible']['lineages'][$x]['remove']);
         }
       }
     }
@@ -1075,7 +1080,7 @@ function _hierarchical_select_process_get_db_selection($element, $hsid, $form_st
  * @see _hierarchical_select_hierarchy_generate()
  * @see _hierarchical_select_dropbox_generate()
  */
-function _hierarchical_select_process_calculate_selections(&$element, $hsid, $form_state) {
+function _hierarchical_select_process_calculate_selections(&$element, $hsid, &$form_state) {
   $hs_selection = array(); // hierarchical select selection
   $db_selection = array(); // dropbox selection
 
@@ -1086,7 +1091,7 @@ function _hierarchical_select_process_calculate_selections(&$element, $hsid, $fo
   // - no input data was provided (through POST nor GET)
   // - or #value is set directly and not by a Hierarchical Select POST (and
   //   therefor set either manually or by another module),
-  // then use the value of #default_value, or when available, of #value.  
+  // then use the value of #default_value, or when available, of #value.
   if (empty($form_state['input']) || (!isset($element['#value']['hierarchical_select']) && !isset($element['#value']['dropbox']))) {
     $value = (!empty($element['#value'])) ? $element['#value'] : $element['#default_value'];
     $value = (is_array($value)) ? $value : array($value);
@@ -1470,7 +1475,7 @@ function _hierarchical_select_mark_as_disabled(&$element) {
   //    for UI purposes only, but still allow input to be processed if it's
   //    sumitted, it can set the desired attribute in #attributes directly
   //    rather than using #disabled."
-  // #disabled prevents #value from containing values for disabled elements, 
+  // #disabled prevents #value from containing values for disabled elements,
   // but using #attributes circumvents this. Most likely, Form API thinks that
   // because HS' selects are disabled, that the whole of HS is disabled (which
   // is of course a wrong assumption). Hence it thinks the 'op' that is being