Validator throws out a data type which the schema processing has accepted

Doctrine accepts 'char' in the (yml) schema, and creates the database and model.
Then an attempt to save a record raises a Doctrine_Validator_Exception, which turns out to contain no validation message, but just the cryptic
[_errors:protected] => Array
(
[nickname] => Array
(
[0] => type
)

)

[_validators:protected] => Array
(
)

Only by looking at the source did I discover that what this means is that the validator does not accept the column type 'char' - because it's not hard-coded in Doctrine_Validator::isValidType.

I've vacillated over whether to classify this as 'Major' or Minor': once I've realised what's going on, it's easy to work round; but it is a show-stopper for a Doctrine novice.