Index: ds.module
===================================================================
--- ds.module	(revision 366)
+++ ds.module	(working copy)
@@ -209,7 +209,9 @@
           'title' => $field['title'],
           'labelformat' => (isset($field_settings[$key]['labelformat'])) ? $field_settings[$key]['labelformat'] : DS_DEFAULT_LABEL_FORMAT,
           'type' => isset($field['display_settings']) ? 'other' : 'ds',
+          'class' => isset($field['properties']['css-class']) ? $field['properties']['css-class'] : 'field-'. strtr($key, '_', '-'),
         );
+
         // Try to change the title if this is configured and label is not hidden.
         if (isset($field_settings[$key]['label_value']) && $ds_fields[$key]['labelformat'] != DS_DEFAULT_LABEL_FORMAT) {
           $ds_fields[$key]['title'] = t(check_plain($field_settings[$key]['label_value']));
@@ -321,8 +323,7 @@
       foreach ($region as $key => $weight) {
         $field_content = isset($vars[$key .'_rendered']) ? $vars[$key .'_rendered'] : '';
         if (!empty($field_content)) {
-          $field_key = strtr($key, '_', '-');
-          $region_content .= theme($theme_function, $field_content, $field_key, $object->ds_fields[$key]);
+          $region_content .= theme($theme_function, $field_content, $object->ds_fields[$key]);
         }
       }
 
Index: theme/theme.inc
===================================================================
--- theme/theme.inc	(revision 366)
+++ theme/theme.inc	(working copy)
@@ -10,15 +10,14 @@
  * Theme function to render the field content.
  *
  * @param string $content The content to render.
- * @param string $field_key The name of the field key.
  * @param array $field The current field.
  */
-function theme_ds_field($content, $field_key, $field) {
+function theme_ds_field($content, $field) {
 
   $output = '';
   if (!empty($content)) {
     if ($field['type'] == 'ds') {
-      $output .= '<div class="field field-'. $field_key .'">';
+      $output .= '<div class="field '. $field['class'] .'">';
       // Above label.
       if ($field['labelformat'] == 'above') {
         $output .= '<div class="field-label">'. $field['title'] .': </div>';