FPC interfaces bug

program fpc_bug;
{$mode objfpc}
{$interfaces CORBA}
uses Variants;

type
IInterfaceA = interface
  procedure Afunction( x : byte );
end;

IInterfaceB = interface
  procedure Bfunction( s : AnsiString );
end;

TBaseObject = class(IInterfaceA)
  procedure Afunction( x : byte ); // implemented from IInterfaceA
end;

TOtherObject = class(TBaseObject, IInterfaceB)
  procedure Bfunction( s : AnsiString ); // implemented from IInterfaceB
end;

procedure TBaseObject.Afunction( x : byte );
begin
  Writeln('TBaseObject : ', x );
end;

procedure TOtherObject.Bfunction( s : AnsiString );
begin
  Writeln('TOtherObject : ', s );
end;

var oo : TOtherObject;
    o  : TObject;
begin
  oo := TOtherObject.Create;
  o := oo;
  (o as IInterfaceA).AFunction(42);
end.