RTL-RTX example complie error

When I compile the Mailbox example of RTL-RTX, I got a error message:

main.c(36): error: #167: argument of type "U32 **" is incompatible with parameter of type "void **"

Why? How can I resolve this problem?
Thanks.

Here is the source code:

#include <RTL.h>
...
void rec_task(void) __task
{
    /* This task will receive a message.        */
    U32 *rptr, rec_val[2];

    os_mbx_wait(MsgBox, &rptr, 0xffff);  /* error! */
    rec_val[0] = rptr[0];
    rec_val[1] = rptr[1];
    _free_box(mpool, rptr);
    os_tsk_delete_self();
}