diff --git a/handlers/views_handler_field.inc b/handlers/views_handler_field.inc
index 5578fbb..24348bc 100644
--- a/handlers/views_handler_field.inc
+++ b/handlers/views_handler_field.inc
@@ -241,8 +241,11 @@ class views_handler_field extends views_handler {
    * Return the class of the field.
    */
   function element_classes($row_index = NULL) {
-    $classes = explode(' ', $this->tokenize_value($this->options['element_class'], $row_index));
-    $classes = array_map('drupal_clean_css_identifier', $classes);
+    $classes = explode(' ', $this->options['element_class']);
+    foreach ($classes as &$class) {
+      $class = $this->tokenize_value($class, $row_index);
+      $class = views_clean_css_identifier($class);
+    }
     return implode(' ', $classes);
   }
 
@@ -289,7 +292,10 @@ class views_handler_field extends views_handler {
    */
   function element_label_classes() {
     $classes = explode(' ', $this->options['element_label_class']);
-    $classes = array_map('drupal_clean_css_identifier', $classes);
+    foreach ($classes as &$class) {
+      $class = $this->tokenize_value($class);
+      $class = views_clean_css_identifier($class);
+    }
     return implode(' ', $classes);
   }
 
@@ -298,7 +304,10 @@ class views_handler_field extends views_handler {
    */
   function element_wrapper_classes() {
     $classes = explode(' ', $this->options['element_wrapper_class']);
-    $classes = array_map('drupal_clean_css_identifier', $classes);
+    foreach ($classes as &$class) {
+      $class = $this->tokenize_value($class);
+      $class = views_clean_css_identifier($class);
+    }
     return implode(' ', $classes);
   }
 
diff --git a/plugins/views_plugin_display.inc b/plugins/views_plugin_display.inc
index 7ffa70d..2819bd4 100644
--- a/plugins/views_plugin_display.inc
+++ b/plugins/views_plugin_display.inc
@@ -1881,7 +1881,7 @@ class views_plugin_display extends views_plugin {
     switch ($form_state['section']) {
       case 'css_class':
         $css_class = $form_state['values']['css_class'];
-        if (preg_match('/[^a-zA-Z0-9- ]/', $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.'));
         }
       break;
diff --git a/theme/theme.inc b/theme/theme.inc
index 04b92b9..4fa75c3 100644
--- a/theme/theme.inc
+++ b/theme/theme.inc
@@ -678,10 +678,10 @@ function template_preprocess_views_view_list(&$vars) {
   $handler  = $vars['view']->style_plugin;
 
   $class = explode(' ', $handler->options['class']);
-  $class = array_map('drupal_clean_css_identifier', $class);
+  $class = array_map('views_clean_css_identifier', $class);
 
   $wrapper_class = explode(' ', $handler->options['wrapper_class']);
-  $wrapper_class = array_map('drupal_clean_css_identifier', $wrapper_class);
+  $wrapper_class = array_map('views_clean_css_identifier', $wrapper_class);
 
   $vars['class'] = implode(' ', $class);
   $vars['wrapper_class'] = implode(' ', $wrapper_class);
diff --git a/views.module b/views.module
index 81bae5a..32bdf22 100644
--- a/views.module
+++ b/views.module
@@ -1782,6 +1782,39 @@ function views_var_export($var, $prefix = '', $init = TRUE) {
 }
 
 /**
+ * Prepare a string for use as a valid CSS identifier (element, class or ID name).
+ * This function is similar to a core version but with more sane filter values.
+ *
+ * http://www.w3.org/TR/CSS21/syndata.html#characters shows the syntax for valid
+ * CSS identifiers (including element names, classes, and IDs in selectors.)
+ *
+ * @param $identifier
+ *   The identifier to clean.
+ * @param $filter
+ *   An array of string replacements to use on the identifier.
+ * @return
+ *   The cleaned identifier.
+ *
+ * @see drupal_clean_css_identifier
+ */
+function views_clean_css_identifier($identifier, $filter = array(' ' => '-', '/' => '-', '[' => '-', ']' => '')) {
+  // By default, we filter using Drupal's coding standards.
+  $identifier = strtr($identifier, $filter);
+
+  // Valid characters in a CSS identifier are:
+  // - the hyphen (U+002D)
+  // - a-z (U+0030 - U+0039)
+  // - A-Z (U+0041 - U+005A)
+  // - the underscore (U+005F)
+  // - 0-9 (U+0061 - U+007A)
+  // - ISO 10646 characters U+00A1 and higher
+  // We strip out any character not in the above list.
+  $identifier = preg_replace('/[^\x{002D}\x{0030}-\x{0039}\x{0041}-\x{005A}\x{005F}\x{0061}-\x{007A}\x{00A1}-\x{FFFF}]/u', '', $identifier);
+
+  return $identifier;
+}
+
+/**
  * Implement hook_views_exportables().
  */
 function views_views_exportables($op = 'list', $views = NULL, $name = 'foo') {