Firebird 2.5 + EF6, how to set transaction to wait

How can I set transactions in EF6 with firebird provider 4.0 EF6 to wait. Default is no wait, so I get a lot of exceptions.

To set the transaction isolation level, I use dbContext.Database.StartTransaction(). I try to use isolation level serializable to serialize the access to one table. I only read a value, add a constant and write that new value back.

I always got the exception lock conflict on no wait transaction, that's why I want to use a transaction that wait until the other has ended.