diff --git a/plugins/views_plugin_display.inc b/plugins/views_plugin_display.inc
index b7aa6cee..52ab345d 100644
--- a/plugins/views_plugin_display.inc
+++ b/plugins/views_plugin_display.inc
@@ -2233,8 +2233,8 @@ class views_plugin_display extends views_plugin {
         break;
       case 'css_class':
         $css_class = $form_state['values']['css_class'];
-        if (preg_match('/[^a-zA-Z0-9-_ ]/', $css_class)) {
-          form_error($form['css_class'], t('CSS classes must be alphanumeric or dashes only.'));
+        if (preg_match('/[^[:alnum:]-_ ]/', $css_class)) {
+          form_error($form['css_class'], t('CSS classes must be alphanumeric, dashes, or underscores only.'));
         }
       break;
       case 'display_id':
diff --git a/plugins/views_plugin_style.inc b/plugins/views_plugin_style.inc
index 5bd70866..a4cf1c08 100644
--- a/plugins/views_plugin_style.inc
+++ b/plugins/views_plugin_style.inc
@@ -139,7 +139,7 @@ class views_plugin_style extends views_plugin {
 
       // Convert whatever the result is to a nice clean class name
       foreach ($classes as &$class) {
-        $class = drupal_clean_css_identifier($class);
+        $class = views_clean_css_identifier($class);
       }
       return implode(' ', $classes);
     }
diff --git a/theme/theme.inc b/theme/theme.inc
index befd4d1a..221895a0 100644
--- a/theme/theme.inc
+++ b/theme/theme.inc
@@ -63,7 +63,7 @@ function template_preprocess_views_view(&$vars) {
 
   $css_class = $view->display_handler->get_option('css_class');
   if (!empty($css_class)) {
-    $vars['css_class'] = preg_replace('/[^a-zA-Z0-9- ]/', '-', $css_class);
+    $vars['css_class'] = preg_replace('/[^[:alnum:]_ ]/', '-', $css_class);
     $vars['classes_array'][] = $vars['css_class'];
   }