diff --git a/modules/block/block.install b/modules/block/block.install
index deed13a..34a276f 100644
--- a/modules/block/block.install
+++ b/modules/block/block.install
@@ -137,7 +137,7 @@ function block_schema() {
         'type' => 'serial',
         'unsigned' => TRUE,
         'not null' => TRUE,
-        'description' => "The block's {block}.bid.",
+        'description' => 'The custom block ID, which is used as the {block}.delta value.',
       ),
       'body' => array(
         'type' => 'text',
@@ -185,3 +185,15 @@ function block_install() {
     ->condition('name', 'block')
     ->execute();
 }
+
+/**
+ * Update the description of {block_custom}.bid.
+ */
+function block_update_8000() {
+  db_change_field('block_custom', 'bid', 'bid', array(
+    'type' => 'serial',
+    'unsigned' => TRUE,
+    'not null' => TRUE,
+    'description' => 'The custom block ID, which is used as the {block}.delta value.',
+  ));
+}