diff --git modules/block/block.module modules/block/block.module
index 27e31bc..0330eb9 100644
--- modules/block/block.module
+++ modules/block/block.module
@@ -559,7 +559,7 @@ function block_form_user_profile_form_alter(&$form, &$form_state) {
         $blocks[$block->module][$block->delta] = array(
           '#type' => 'checkbox',
           '#title' => check_plain($data[$block->delta]['info']),
-          '#default_value' => isset($account->block[$block->module][$block->delta]) ? $account->block[$block->module][$block->delta] : ($block->custom == 1),
+          '#default_value' => isset($account->data['block'][$block->module][$block->delta]) ? $account->data['block'][$block->module][$block->delta] : ($block->custom == 1),
         );
       }
     }
@@ -579,6 +579,15 @@ function block_form_user_profile_form_alter(&$form, &$form_state) {
 }
 
 /**
+ * Implements hook_user_presave().
+ */
+function block_user_presave(&$edit, $account, $category) {
+  if (isset($edit['block'])) {
+    $edit['data']['block'] = $edit['block'];
+  }
+}
+
+/**
  * Initialize blocks for enabled themes.
  */
 function block_themes_enabled($theme_list) {
@@ -741,8 +750,8 @@ function block_block_list_alter(&$blocks) {
 
     // Use the user's block visibility setting, if necessary.
     if ($block->custom != BLOCK_CUSTOM_FIXED) {
-      if ($user->uid && isset($user->block[$block->module][$block->delta])) {
-        $enabled = $user->block[$block->module][$block->delta];
+      if ($user->uid && isset($user->data['block'][$block->module][$block->delta])) {
+        $enabled = $user->data['block'][$block->module][$block->delta];
       }
       else {
         $enabled = ($block->custom == BLOCK_CUSTOM_ENABLED);
diff --git modules/block/block.test modules/block/block.test
index db8a257..458d514 100644
--- modules/block/block.test
+++ modules/block/block.test
@@ -188,6 +188,57 @@ class BlockTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Test user customization of block visibility.
+   */
+  function testBlockVisibilityPerUser() {
+    $block = array();
+
+    // Create a random title for the block.
+    $title = $this->randomName(8);
+
+    // Create our custom test block.
+    $custom_block = array();
+    $custom_block['info'] = $this->randomName(8);
+    $custom_block['title'] = $title;
+    $custom_block['body[value]'] = $this->randomName(32);
+    $this->drupalPost('admin/structure/block/add', $custom_block, t('Save block'));
+
+    $bid = db_query("SELECT bid FROM {block_custom} WHERE info = :info", array(':info' => $custom_block['info']))->fetchField();
+    $block['module'] = 'block';
+    $block['delta'] = $bid;
+    $block['title'] = $title;
+
+    // Move block to the first sidebar.
+    $this->moveBlockToRegion($block, $this->regions[1]);
+
+    // Set the block to be customizable per user, visible by default.
+    $edit = array();
+    $edit['custom'] = BLOCK_CUSTOM_ENABLED;
+    $this->drupalPost('admin/structure/block/manage/' . $block['module'] . '/' . $block['delta'] . '/configure', $edit, t('Save block'));
+
+    // Disable block visibility for the admin user.
+    $edit = array();
+    $edit['block[' . $block['module'] . '][' . $block['delta'] . ']'] = FALSE;
+    $this->drupalPost('user/' . $this->admin_user->uid . '/edit', $edit, t('Save'));
+
+    $this->drupalGet('');
+    $this->assertNoText($block['title'], t('Block was not displayed according to per user block visibility setting.'));
+
+    // Set the block to be customizable per user, hidden by default.
+    $edit = array();
+    $edit['custom'] = BLOCK_CUSTOM_DISABLED;
+    $this->drupalPost('admin/structure/block/manage/' . $block['module'] . '/' . $block['delta'] . '/configure', $edit, t('Save block'));
+
+    // Enable block visibility for the admin user.
+    $edit = array();
+    $edit['block[' . $block['module'] . '][' . $block['delta'] . ']'] = TRUE;
+    $this->drupalPost('user/' . $this->admin_user->uid . '/edit', $edit, t('Save'));
+
+    $this->drupalGet('');
+    $this->assertText($block['title'], t('Block was displayed according to per user block visibility setting.'));
+  }
+
+  /**
    * Test configuring and moving a module-define block to specific regions.
    */
   function testBlock() {