diff --git a/install.php b/install.php
index 87e3eddf..334e2f69 100644
--- a/install.php
+++ b/install.php
@@ -597,29 +597,10 @@ if (file_exists($config['has_installed'])) {
             foreach ($boards as &$board)
                 query(sprintf("ALTER TABLE ``posts_%s`` ADD `cycle` int(1) NOT NULL AFTER `locked`", $board['uri'])) or error(db_error());
 		case '5.1.2':
-			query('CREATE TABLE IF NOT EXISTS ``nntp_references`` (
-				  `board` varchar(60) NOT NULL,
-				  `id` int(11) unsigned NOT NULL,
-				  `message_id` varchar(255) CHARACTER SET ascii NOT NULL,
-				  `message_id_digest` varchar(40) CHARACTER SET ascii NOT NULL,
-				  `own` tinyint(1) NOT NULL,
-				  `headers` text,
-				  PRIMARY KEY (`message_id_digest`),
-				  UNIQUE KEY `message_id` (`message_id`),
-				  UNIQUE KEY `u_board_id` (`board`, `id`)
-				) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
-			') or error(db_error());
 		case '5.1.3':
-			query('CREATE TABLE IF NOT EXISTS ``captchas`` (
-			  	`cookie` varchar(50),
-			  	`extra` varchar(200),
-			  	`text` varchar(255),
-			  	`created_at` int(11),
-			  	PRIMARY KEY (`cookie`,`extra`)
-				) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4;') or error(db_error());
 		case '5.2.0-dev-1':
-			query('DROP TABLE IF EXISTS ``nntp_references``;
-				   DROP TABLE IF EXISTS ``captchas``;') or error(db_error());
+			query('DROP TABLE IF EXISTS ``nntp_references``;') or error(db_error());
+			query('DROP TABLE IF EXISTS ``captchas``;') or error(db_error());
 		case false:
 			// TODO: enhance Tinyboard -> vichan upgrade path.
 			query("CREATE TABLE IF NOT EXISTS ``search_queries`` (  `ip` varchar(39) NOT NULL,  `time` int(11) NOT NULL,  `query` text NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=utf8;") or error(db_error());