=== modified file 'modules/block/block.module'
--- modules/block/block.module	
+++ modules/block/block.module	
@@ -687,6 +687,18 @@ function block_list($region) {
         }
       }
     }
+
+    $all_blocks = array();
+    // Create a reference array of block info to pass to hook_block_alter.
+    foreach ($blocks as $region_id => $region_data) {
+      foreach ($region_data as $block_id => $block_data) {
+        $all_blocks[$block_id] =& $blocks[$region_id][$block_id];
+      }
+    }
+    foreach (module_implements('block_alter') as $module) {
+      $function = $module .'_block_alter';
+      $function($all_blocks);
+    }
   }
   // Create an empty array if there were no entries
   if (!isset($blocks[$region])) {