declare typedef type

struct mystruct
{
    int   i;
    double f;
} ;

typedef mystruct myotherstruct;

//the other .cpp file
struct mystruct;  //OK,this is a correct forward declaration.
struct myotherstruct; // error C2371（in vc2k8）: 'myotherstruct' : redefinition; different basic types

Hi all. Why can't I forward declare myotherstruct?