Using FMDB to Rollback Transactions in Swift

So I am trying to use FMDB in Swift. I have everything hooked up fine as far as bridging headers and such, but I can't for the life of me figure out how to use transactions in the FMDatabaseQueue class. Specifically I do not understand the syntax to rollback a transaction. I have tried the code below but it yields a compile time error of

'UnsafeMutablePointer<ObjCBool>' does not have a member named 'initialize'

I am sure this has to do with the fact that a pointer is being passed into the closure for rollback, but as far as I am aware you cannot reassign variables passed into closures in swift, so I'm not sure how I am suppose to set the pointer to indicate a rollback is needed.

if let queue = FMDatabaseQueue(path: DB_PATH) {
    queue.inTransaction() {
        db, rollback in

        // This could be any statement, drop table is just an example
        success = db.executeUpdate("DROP TABLE test", withArgumentsInArray:nil)

        if !success {
            // Need to rollback here
            rollback.initalize(true)
            return
        }
    }
}

What do I need to do to indicate a rollback?