nullable char field is not handled correctly by ExpressionBuilder

I have an Oracle database and I was executing LINQ select from a table. Filter expression was on a nullable char field. 

I had an expression like

var q = Db.Table.Where(x => x.Field == 'Y')

and it was translated into something like

SELECT
*
FROM Table 
WHERE Field=89

note that 'Y' was translated into 89 and obviously Oracle did not accept it.