FullText & Join index

I have one table with a full text index, and another table to which I need to join, based on an ID field in the fulltext table. I can't get the join query to use non-fulltext table's index to do a ref join; it insists on doing an index scan on the second table. Is there any way to avoid the index scan?

The query is
SELECT
dm.MessageID, sm.DBID
FROM
tdistinctmessages dm,
tSite_messages sm
WHERE MATCH (dm.message) AGAINST ('"microsoft support"' IN BOOLEAN MODE)
AND dm.MessageID=sm.MessageID

Table definitions are:

CREATE TABLE `tdistinctmessages` (
  `message` VARCHAR(150) COLLATE latin1_general_ci NOT NULL,
  `MessageID` INT(10) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY  (`message`,`MessageID`),
  FULLTEXT KEY `FTIX_Message` (`message`)
) ENGINE=MYISAM AUTO_INCREMENT=26935581 DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci


CREATE TABLE `tsite_messages` (
  `DBID` INT(10) NOT NULL,
  `wordID` BIGINT(20) UNSIGNED DEFAULT NULL,
  `MessageID` INT(10) DEFAULT NULL,
  `Repetition` INT(10) NOT NULL DEFAULT '0',
  `Emphasis` INT(10) NOT NULL DEFAULT '0',
  KEY `IX_DBID_WordID_MessageID_Repetition` (`DBID`,`wordID`,`MessageID`,`Repetition`),
  KEY `NewIndex1` (`MessageID`,`DBID`,`Repetition`)
) ENGINE=MYISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci

EXPLAIN IS

      possible_keys      key      key_len      ref      rows      Extra
1      SIMPLE      dm      fulltext      FTIX_Message      FTIX_Message      0            1      Using where
1      SIMPLE      sm      index      NewIndex1      NewIndex1      13      \N      27892950      Using where; Using index