Could not cast value of type '__NSDictionaryM'

When I run RaiseMan and select “add Employee” the call to the func addEmployer reaches the following line it aborts thread 1 with the message below

    // Create the object
    let employee = arrayController.newObject() as! Employee

Could not cast value of type ‘__NSDictionaryM’ (0x7fff7df9c460) to ‘RaiseMan.Employee’ (0x1000180e0).

I checked the book and the file on this site and even rewrote it a couple of times. I suspect that the problem is with another file or elsewhere in Document.swift but I have no clue as to where to look.