E2170 Cannot override a non-virtual method on Updating DSharp

Question

I am trying to update DSharp to the latest release. Before doing that I updated Spring4D successfully.

When I tried to update DSharp and build DSharp.Core.DelphiXE2.bpl I had the error message

"[DCC Error] DSharp.Collections.Iterators.pas(54): E2170 Cannot override a non-virtual method"

Here below is the excerpt of the unit with line 54

TCustomIterator<T> = class(TIterator<T>)
  private
    fProc: TIteratorProc<T>;
  public
    constructor Create(const proc: TIteratorProc<T>);

    function Clone: TIterator<T>; override;
    function MoveNext: Boolean; override; // line 54
  end;

Any idea of what I am missing out on?

My machine runs a Win 7, 32-bit

Many thanks Alberto