Watch Dog Reset

For a long time now I’ve used the following code to reset the arduino uno and mega boards:

void Reboot()
{
  wdt_enable(WDTO_15MS);
  while(1)
  {
    // Nothing to do but wait
  }
}

I’ve recently gotten a batch of Chinese boards that this does not work on. I just spin forever in the while(1) loop

I’ve replaced it with this code:

void Reboot()
{
  asm volatile("jmp 0"); 
}

but I really prefer the watch dog way as its more of a hard reboot. Anybody have any ideas on why the watch dog wouldn’t work?

Thanks
Dave