Swift 3 Bindings question

Since migrating to Swift 3, I get an error in Interface Builder.

Error: "The Content Array binding expects to be bound to an object of type NSObject, but self.scientists is of type Scientist"

This is the stored property in the Viewcontroller to which the arrayController is bound.

dynamic var scientists:[Scientist] = [Scientist]()

and populated in ViewDidLoad by:

self.scientists.append(Scientist(name:"Albert Einstein"))

Class Scientist is simply this.

class Scientist: NSObject {
  
    let name:String
  
  
    init(name:String){
      
        self.name = name
    }
  
  
    override convenience init(){
      
        self.init(name:"Not Named")
    }
}

Other than a big red exclamation point in IB, it still compiles and shows no other effect. The tableview is populated correctly as expected. Changing the array in the ViewController to an NSMutableArray removes the red exclamation, as expected.

May I indulge the group as to whether this should simply be ignored ( I think the same code in Swift 2.3 was not flagged) or is there a way to work around this without resorting to changing the array to an NSMutableArray.

Thanks in advance.