Standard Pro Mini Bootloader and Watchdog Reset.

The PRo Mini bootloader, I use the 3.3V 8Mhz one, that comes with the Arduino IDE 1.8.5, does not work correctly when you attemp to uses the Watchdog reset. The simple code below does not reset the Arduino;

#include <avr/wdt.h> // watchdog timer

void setup( void )
{
  Serial.begin(9600); // Serial line is opened. Used mostly for testing.
  Serial.println( F( "Eight seconds and..." ) );
  wdt_enable(WDTO_8S); // we enable the watchdog timer to bite after 8 seconds
}

void loop( void )
{
}

A quick bit of Googling identifies the problem, and the solution is to use the bootloader that comes with Minicore, and indeed the code above does then work, problem solved.

Changing the bootloader is sometimes not convenient, so is there any magic voodoo code to make the watchdog reset work properly with the bootloader in IDE 1.8.5 ?