`React.forwardRef` broken in v12

[cknitt]

This compiles fine in v11 (Playground):

@react.component
let make = React.forwardRef((~className=?, ~children, ref) =>
  <div>
    <input
      type_="text"
      ?className
      ref=?{ref->Nullable.toOption->Option.map(ReactDOM.Ref.domRef)}
    />
    children
  </div>
)

but gives the following error message without LoC in v12 (Playground):

[E] Line 1, column -1:
This function call is incorrect.
  The function has type:
  (
  props<string, React.element, ReactDOM.Ref.currentDomRef>,
  Js.Nullable.t<ReactDOM.Ref.currentDomRef>,
) => Jsx.element
  
  It is called with 2 argument just but requiress 1.

Seems this broke in alpha.6.