diff --git a/modules/field/views_handler_field_field.inc b/modules/field/views_handler_field_field.inc
index 299b5a7..cbf7ba4 100644
--- a/modules/field/views_handler_field_field.inc
+++ b/modules/field/views_handler_field_field.inc
@@ -520,7 +520,7 @@ class views_handler_field_field extends views_handler_field {
     // With "field API" fields, the column target of the grouping function
     // and any additional grouping columns must be specified.
     $group_columns = array(
-      'entity id' => t('Entity ID'),
+      'entity_id' => t('Entity ID'),
     ) + drupal_map_assoc(array_keys($this->field_info['columns']), 'ucfirst');
 
     $form['group_column'] = array(