Index: pm_block_user/pm_block_user.install
===================================================================
RCS file: /cvs/drupal/contributions/modules/privatemsg/pm_block_user/pm_block_user.install,v
retrieving revision 1.2
diff -u -r1.2 pm_block_user.install
--- pm_block_user/pm_block_user.install	30 Nov 2009 17:37:15 -0000	1.2
+++ pm_block_user/pm_block_user.install	12 Feb 2010 19:39:46 -0000
@@ -27,6 +27,7 @@
         'unsigned'      => TRUE,
       ),
     ),
+    'primary key' => array('author', 'recipient'),
   );
 
   return $schema;
@@ -39,3 +40,9 @@
 function pm_block_user_uninstall() {
   drupal_uninstall_schema('pm_block_user');
 }
+
+function pm_block_user_update_6000() {
+  $ret = array();
+  db_add_primary_key($ret, 'pm_block_user', array('author', 'recipient'));
+  return $ret;
+}