diff --git a/phpBB/install/database_update.php b/phpBB/install/database_update.php
index a1b7dcd47f..b6298ca651 100644
--- a/phpBB/install/database_update.php
+++ b/phpBB/install/database_update.php
@@ -2024,6 +2024,48 @@ function change_database_data(&$no_updates, $version)
 		// No changes from 3.0.10-RC3 to 3.0.10
 		case '3.0.10-RC3':
 		break;
+
+		// Changes from 3.0.10 to 3.0.11-RC1
+		case '3.0.10':
+			// Delete orphan private messages
+			$batch_size = 500;
+
+			$sql_array = array(
+				'SELECT'	=> 'p.msg_id',
+				'FROM'		=> array(
+					PRIVMSGS_TABLE	=> 'p',
+				),
+				'LEFT_JOIN'	=> array(
+					array(
+						'FROM'	=> array(PRIVMSGS_TO_TABLE, 't'),
+						'ON'	=> 'p.msg_id = t.msg_id',
+					),
+				),
+				'WHERE'		=> 't.user_id IS NULL';
+			$sql = $db->sql_build_query('SELECT', $sql_array);
+
+			do
+			{
+				$result = $db->sql_query_limit($sql, $batch_size);
+
+				$delete_pms = array();
+				while ($row = $db->sql_fetchrow($result))
+				{
+					$delete_pms[] = (int) $row['msg_id'];
+				}
+				$db->sql_freeresult($result);
+
+				if (!empty($delete_pms))
+				{
+					$sql = 'DELETE FROM ' . PRIVMSGS_TABLE . '
+						WHERE ' . $db->sql_in_set('msg_id', $delete_pms);
+					$db->sql_query($sql);
+				}
+			}
+			while (sizeof($delete_pms) == $batch_size);
+
+			$no_updates = false;
+		break;
 	}
 }