Cardinality violation when searching phrase

Im have setup search behaviour for my model.

Searching phrase "foo bar" throws "Doctrine_Connection_Mysql_Exception"

SQLSTATE[21000]: Cardinality violation: 1242 Subquery returns more than 1 row

To fix the issue replace line 208 in file: Doctrine/Search/Query.php

$where .= ' AND (position + ' . $k . ') = (SELECT position FROM ' . $this->_table->getTableName() . ' WHERE ' . $this->parseWord($word) . ')';

with:

$where .= ' AND (position + ' . $k . ') IN (SELECT position FROM ' . $this->_table->getTableName() . ' WHERE ' . $this->parseWord($word) . ')';