diff --git a/menu-block-wrapper.tpl.php b/menu-block-wrapper.tpl.php
index d98bca3..6dc11ea 100644
--- a/menu-block-wrapper.tpl.php
+++ b/menu-block-wrapper.tpl.php
@@ -12,8 +12,8 @@
  * The following variables are provided for contextual information.
  * - $delta: (string) The menu_block's block delta.
  * - $config: An array of the block's configuration settings. Includes
- *   menu_name, parent_mlid, title_link, admin_title, level, follow, depth,
- *   expanded, and sort.
+ *   menu_name, parent_mlid, title_link, admin_title, class_name, level, follow,
+ *   depth, expanded, and sort.
  *
  * @see template_preprocess_menu_block_wrapper()
  */
diff --git a/menu_block.admin.inc b/menu_block.admin.inc
index eda4fd6..a28edbe 100644
--- a/menu_block.admin.inc
+++ b/menu_block.admin.inc
@@ -294,6 +294,12 @@ function menu_block_configure_form($form, &$form_state) {
     '#description' => t('The preferred menus used by <em>&lt;the menu selected by the page&gt;</em> can be customized on the <a href="!url">Menu block settings page</a>.', array('!url' => url('admin/config/user-interface/menu-block'))),
     '#attributes' => array('class' => array('menu-block-menu-name')),
   );
+  $form['class_name'] = array(
+    '#type' => 'textfield',
+    '#default_value' => $config['class_name'],
+    '#title' => t('Additional CSS class name'),
+    '#description' => t('Optionally assign a CSS class name in addition to <strong>menu-block-!delta</strong>.', array('!delta' => $form_state['values']['delta'])),
+  );
   $form['level'] = array(
     '#type' => 'select',
     '#title' => t('Starting level'),
@@ -395,7 +401,7 @@ function menu_block_configure_form($form, &$form_state) {
   $form['menu-block-wrapper-close'] = array('#markup' => '</div>');
 
   // Set visibility of advanced options.
-  foreach (array('title_link', 'follow', 'depth_relative', 'follow_parent', 'expanded', 'sort', 'parent') as $key) {
+  foreach (array('title_link', 'follow', 'depth_relative', 'follow_parent', 'class_name', 'expanded', 'sort', 'parent') as $key) {
     $form[$key]['#states']['visible'][':input[name=display_options]'] = array('value' => 'advanced');
   }
   if ($config['title_link'] || $follow || $config['expanded'] || $config['sort'] || $config['parent_mlid']) {
@@ -440,6 +446,7 @@ function _menu_block_block_save($delta = '', $edit = array()) {
     if (empty($config['exported_to_code'])) {
       variable_set("menu_block_{$delta}_title_link", $edit['title_link']);
       variable_set("menu_block_{$delta}_admin_title", $edit['admin_title']);
+      variable_set("menu_block_{$delta}_class_name", $edit['class_name']);
       variable_set("menu_block_{$delta}_parent", $edit['parent']);
       variable_set("menu_block_{$delta}_level", $edit['level']);
       variable_set("menu_block_{$delta}_follow", $edit['follow']);
diff --git a/menu_block.api.php b/menu_block.api.php
index 491297e..a8b5b65 100644
--- a/menu_block.api.php
+++ b/menu_block.api.php
@@ -37,6 +37,7 @@ function hook_menu_block_blocks() {
       'parent_mlid' => 0,
       'title_link'  => FALSE,
       'admin_title' => 'Drop-down navigation',
+      'class_name'  => 'primary-links-menu-block',
       'level'       => 1,
       'follow'      => 0,
       'depth'       => 2,
diff --git a/menu_block.module b/menu_block.module
index a5bf396..babcadf 100644
--- a/menu_block.module
+++ b/menu_block.module
@@ -191,6 +191,10 @@ function template_preprocess_menu_block_wrapper(&$variables) {
   $variables['classes_array'][] = 'menu-name-' . $variables['config']['menu_name'];
   $variables['classes_array'][] = 'parent-mlid-' . menu_block_clean_css_identifier($variables['config']['parent_mlid']);
   $variables['classes_array'][] = 'menu-level-' . $variables['config']['level'];
+  $classes = explode(' ', $variables['config']['class_name']);
+  foreach ($classes as $class) {
+    $variables['classes_array'][] = drupal_html_class($class);
+  }
 }
 
 /**
@@ -239,6 +243,7 @@ function menu_block_default_config() {
     'parent' => 'main-menu:0',
     'title_link' => 0,
     'admin_title' => '',
+    'class_name' => '',
     'level' => 1,
     'follow' => 0,
     'depth' => 0,
@@ -487,6 +492,7 @@ function menu_block_get_current_page_menu() {
  *     or a simple string.
  *   - admin_title: (string) An optional title to uniquely identify the block on
  *     the administer blocks page.
+ *   - class_name: (string) An additional CSS class to give to the menu block.
  *   - level: (int) The starting level of the tree.
  *   - follow: (string) Specifies if the starting level should follow the
  *     active menu item. Should be set to 0, 'active' or 'child'.
diff --git a/menu_block_export.admin.inc b/menu_block_export.admin.inc
index 8e487b8..f0a1745 100644
--- a/menu_block_export.admin.inc
+++ b/menu_block_export.admin.inc
@@ -78,6 +78,7 @@ function menu_block_export_form_submit(&$form, &$form_state) {
       'parent'      => {$config['parent']},
       'title_link'  => {$config['title_link']},
       'admin_title' => '{$config['admin_title']}',
+      'class_name' => '{$config['class_name']}',
       'level'       => {$config['level']},
       'follow'      => '{$config['follow']}',
       'depth'       => {$config['depth']},