nested query doesn't work on 4.0.20

[Zhiliang Hu]

I am running MySQL 4.0.20.

Here is my query 1, which works:

mysql> select max(updated) from map_ref;
+--------------+
| max(updated) |
+--------------+
| 2005-05-12 |
+--------------+
1 row in set (0.02 sec)

However when I put it in a nested query it complains:

mysql> select updated from map_ref where updated = (select max(updated) from map_ref);
ERROR 1064: You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'select max(updated) from map_ref)' at line 1

Any suggestion what could be the problem?

Zhiliang