diff --git modules/block/block.module modules/block/block.module
index d2287f4..e293d30 100644
--- modules/block/block.module
+++ modules/block/block.module
@@ -777,7 +777,12 @@ function template_preprocess_block(&$variables) {
   // Create the $content variable that templates expect.
   $variables['content'] = $variables['elements']['#children'];
 
+  if (is_array($variables['#attributes']['class'])) {
+    $variables['classes_array'] = $variables['#attributes']['class'];
+  }
+  unset($variables['#attributes']['class']);
   $variables['classes_array'][] = 'block-' . $variables['block']->module;
+  $variables['extra_attributes'] = $variables['#attributes'] ? ' ' . drupal_attributes($variables['#attributes']) : '';
 
   $variables['template_files'][] = 'block-' . $variables['block']->region;
   $variables['template_files'][] = 'block-' . $variables['block']->module;
diff --git modules/block/block.tpl.php modules/block/block.tpl.php
index 74c8811..e2fb9ca 100644
--- modules/block/block.tpl.php
+++ modules/block/block.tpl.php
@@ -35,7 +35,7 @@
  * @see template_process()
  */
 ?>
-<div id="block-<?php print $block->module . '-' . $block->delta; ?>" class="<?php print $classes; ?>">
+<div id="block-<?php print $block->module . '-' . $block->delta; ?>" class="<?php print $classes; ?>"<?php print $extra_attributes; ?>>
 <?php if ($block->subject): ?>
   <h2><?php print $block->subject ?></h2>
 <?php endif;?>