MyBB SQL Error

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
1064 - syntax error, unexpected '-'
Query:
SELECT t.*, t.username AS threadusername, u.username, MATCH (t.subject) AGAINST ('درخت جستجوی دودویی -- دولتی 74*' in boolean mode) AS relevance FROM mybb_threads t LEFT JOIN mybb_users u ON (u.uid = t.uid) WHERE t.tid <> 12697 AND t.visible=1 AND t.closed NOT LIKE 'moved|%' AND MATCH (t.subject) AGAINST ('درخت جستجوی دودویی -- دولتی 74*' in boolean mode) >= 3 ORDER BY t.lastpost DESC LIMIT 0, 10