Leeds set up an FA Cup tie at home to Tottenham after coming from behind to dump out Birmingham 2-1 in their third-round replay.
Wade Elliott put Blues ahead shortly after the half-hour mark, just as he had done in the initial meeting which finished 1-1 10 days ago.
But once again Leeds levelled after the break, this time courtesy of Ross McCormack's first goal since September - an effort which had not looked like coming with 19-goal striker Luciano Becchio missing due to illness.
El-Hadji Diouf, celebrating his 32nd birthday, then quickly completed the turnaround, keeping his cool to chip home from the penalty spot after Paul Robinson had been penalised for handball.
It means Leeds will now host Spurs in the fourth round of the competition in a televised clash next Sunday, denying cash-strapped Birmingham the chance to pick up a welcome sum in the region of £200,000.