Extension class throws an Internal error on compile

IDE: Visual Studio X
Version: 9.0
Target (If relevant): Island
Description:
extension class throws an Internal error on compile:

    type
    Bytes = array of Byte;
    BytesExtension = public extension class(Bytes)
      method setI16(pos: Integer; v: Integer); inline;
      begin
        self[pos]:= v;
        self[pos +  1]:= v shr 8;
      end;
      method getI16(pos: Integer): Integer; inline;
      begin
        result:= (Integer(self[pos+1]) shl 8) or self[pos];
      end;
    end;
    Program = class
    public  
      class method Main(args: array of String): Int32;
      begin
        var b:= new Bytes(10);
        b.setI16(0,1024);
        writeLn(b.getI16(0));
      end;
    end;

Expected Behavior:
compile without error - works on .NET

Actual Behavior:
return with error:
Schweregrad Code Beschreibung Projekt Datei Zeile Quelle Unterdrückungszustand
Fehler (E0) Internal error: Der Objektverweis wurde nicht auf eine Objektinstanz festgelegt. IslandBug 0 Build

Steps:

Thanks, logged as bugs://76853

bugs://76853 got closed with status fixed.

Logged as bugs://i64653.

bugs://i64653 was closed as fixed.