diff --git a/phpBB/phpbb/db/migration/data/v33x/fix_enable_magic_url.php b/phpBB/phpbb/db/migration/data/v33x/fix_enable_magic_url.php
new file mode 100644
index 0000000000..10e862fcbd
--- /dev/null
+++ b/phpBB/phpbb/db/migration/data/v33x/fix_enable_magic_url.php
@@ -0,0 +1,146 @@
+<?php
+/**
+ *
+ * This file is part of the phpBB Forum Software package.
+ *
+ * @copyright (c) phpBB Limited <https://www.phpbb.com>
+ * @license GNU General Public License, version 2 (GPL-2.0)
+ *
+ * For full copyright and license information, please see
+ * the docs/CREDITS.txt file.
+ *
+ */
+
+namespace phpbb\db\migration\data\v33x;
+
+class fix_enable_magic_url extends \phpbb\db\migration\migration
+{
+	public static function depends_on()
+	{
+		return [
+			'\phpbb\db\migration\data\v330\v330',
+		];
+	}
+
+	public function update_data()
+	{
+		return [
+			['custom', [[$this, 'disable_magic_urls']]],
+			['custom', [[$this, 'update_posts']]],
+			['custom', [[$this, 'update_privmsgs']]],
+		];
+	}
+
+	/**
+	 * Sets all enable_magic_url data to 0 in posts and private messages
+	 *
+	 * @return void
+	 */
+	public function disable_magic_urls()
+	{
+		// Nothing to do if allow_post_links is enabled
+		if ($this->config['allow_post_links'])
+		{
+			return;
+		}
+
+		$sql = 'UPDATE ' . $this->table_prefix . 'posts SET enable_magic_url = 0';
+		$this->sql_query($sql);
+
+		$sql = 'UPDATE ' . $this->table_prefix . 'privmsgs SET enable_magic_url = 0';
+		$this->sql_query($sql);
+	}
+
+	/**
+	 * Perform an update of enable_magic_url in posts
+	 *
+	 * @param int $start Limit start value
+	 * @return int|void  Null if update is finished, next start value if not
+	 */
+	public function update_posts($start)
+	{
+		// Nothing to do if allow_post_links is enabled
+		if ($this->config['allow_post_links'])
+		{
+			return;
+		}
+
+		return $this->update_magic_urls('posts', $start);
+	}
+
+	/**
+	 * Perform an update of enable_magic_url in private messages
+	 *
+	 * @param int $start Limit start value
+	 * @return int|void  Null if update is finished, next start value if not
+	 */
+	public function update_privmsgs($start)
+	{
+		// Nothing to do if allow_post_links is enabled
+		if ($this->config['allow_post_links'])
+		{
+			return;
+		}
+
+		return $this->update_magic_urls('privmsgs', $start);
+	}
+
+	/**
+	 * Update enable_magic_url = 1 for messages that have rendered URLs in them
+	 *
+	 * @param string $table Name of table
+	 * @param int $start Limit start value
+	 * @return int|void Null if update is finished, next start value if not
+	 */
+	public function update_magic_urls($table, $start)
+	{
+		$start = (int) $start;
+		$limit = 100;
+		$updated_items = 0;
+
+		$columns = [
+			'posts'	=> [
+				'item_id'	=> 'post_id',
+				'item_txt'	=> 'post_text',
+			],
+			'privmsgs'	=> [
+				'item_id'	=> 'msg_id',
+				'item_txt'	=> 'message_text',
+			],
+		];
+
+		$sql = "SELECT {$columns[$table]['item_id']} AS id, {$columns[$table]['item_txt']} AS text
+			FROM " . $this->table_prefix . $table;
+		$result = $this->db->sql_query_limit($sql, $limit, $start);
+
+		$items = [];
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			$updated_items++;
+
+			// Look for <!-- m --> or for a URL tag that's not immediately followed by <s>
+			if (strpos($row['text'], '<!-- m -->') !== false || preg_match('(<URL [^>]++>(?!<s>))', $row['text']))
+			{
+				$items[] = (int) $row['id'];
+			}
+		}
+		$this->db->sql_freeresult($result);
+
+		if (count($items))
+		{
+			$sql = 'UPDATE ' . $this->table_prefix . $table . '
+				SET enable_magic_url = 1
+				WHERE ' . $this->db->sql_in_set($columns[$table]['item_id'], $items);
+			$this->sql_query($sql);
+		}
+
+		if ($updated_items < $limit)
+		{
+			// There are no more items to be converted
+			return;
+		}
+
+		// There are still more items to query, return the next start value
+		return $start + $limit;
+	}
+}