diff --git a/modules/block/block.module b/modules/block/block.module
index 2977ca8..7f88f8c 100644
--- a/modules/block/block.module
+++ b/modules/block/block.module
@@ -1009,6 +1009,9 @@ function template_preprocess_block(&$variables) {
 
   $variables['classes_array'][] = drupal_html_class('block-' . $variables['block']->module);
 
+  // Add default class for block content.
+  $variables['content_attributes_array']['class'][] = 'content';
+
   $variables['theme_hook_suggestions'][] = 'block__' . $variables['block']->region;
   $variables['theme_hook_suggestions'][] = 'block__' . $variables['block']->module;
   // Hyphens (-) and underscores (_) play a special role in theme suggestions.
diff --git a/modules/block/block.test b/modules/block/block.test
index 99c81dc..15c090e 100644
--- a/modules/block/block.test
+++ b/modules/block/block.test
@@ -747,8 +747,11 @@ class BlockTemplateSuggestionsUnitTest extends DrupalUnitTestCase {
     $variables2 = array();
     $variables2['elements']['#block'] = $block2;
     $variables2['elements']['#children'] = '';
+    // Test adding a class to the block content.
+    $variables2['content_attributes_array']['class'][] = 'test-class';
     template_preprocess_block($variables2);
     $this->assertEqual($variables2['theme_hook_suggestions'], array('block__footer', 'block__block', 'block__block__hyphen_test'), 'Hyphens (-) in block delta were replaced by underscore (_)');
+    $this->assertEqual($variables2['content_attributes_array']['class'], array('test-class', 'content'), t('Default .content class added to block content_attributes_array'));
   }
 }
 
diff --git a/modules/block/block.tpl.php b/modules/block/block.tpl.php
index f0bfa5c..78387a8 100644
--- a/modules/block/block.tpl.php
+++ b/modules/block/block.tpl.php
@@ -52,7 +52,7 @@
 <?php endif;?>
   <?php print render($title_suffix); ?>
 
-  <div class="content"<?php print $content_attributes; ?>>
+  <div<?php print $content_attributes; ?>>
     <?php print $content ?>
   </div>
 </div>