The Stormers remained on top of the South African Super Rugby conference when they beat the Bulls 14-19 at Loftus Versfeld on Saturday.
The result means that the Stormers have beaten the Bulls twice this season after they also won 20-17 at Newlands in March.
Both teams scored one try each although the Bulls were fortunate to be awarded their try by captain Pierre Spies.
Replays showed that Spies failed to ground the ball correctly but referee Jonathan Kaplan asked TMO Shaun Veldsman if he could award the try in such a way that he could not mention the grounding.
The result moves the Stormers five points clear of the Bulls in the South African conference and the Bulls remain four points ahead the Sharks.
It initially looked like the Bulls found the recipe to getting past the Stormers' near impenetrable defence but a late Bryan Habana try saw the Bulls losing the North-South derby.
The Bulls mauled and bashed their way over the advantage line with the Stormers' renowned defence unable to stop the Bulls.
As the match progressed the Bulls' tactics frustrated the visitors as mistakes crept into their game with penalties also going against them.
The first half was an even affair with the two sides sharing possession evenly.
The Stormers struck the first blow 10 minutes into the match with flyhalf Peter Grant succeeding with a penalty conversion.
The Bulls, however, returned the favour four minutes later with Morne Steyn also converting his penalty kick.
On the 20 minute the Stormers wrestled back the lead with Grant slotting over a penalty.
Up to this point the Bulls followed the kick-and-chase game plan with little effect and switched to the more direct approach.
This proved to be fruitful as Bulls skipper Pierre Spies bashed his way over the try line in the 28th minute with Steyn missing the conversion.
The last minutes of the first half ticked over with both sides converting penalties to take the half-time scores to 11-9 in the Bulls' favour.
After the break the Bulls got back on the score sheet with Steyn succeeding with another penalty conversion.
The Bulls seemed to be secure in the driving seat and smothered the Stormers of both possession and field position.
The Pretoria-based side was presented with a golden opportunity to take the match away from the Stormers with the visitors' prop Frans Malherbe receiving a yellow card for a dangerous tackle.
They could, however, not convert this opportunity into points and instead of extending their lead they gave away a penalty which Grant converted.
The Bulls inability to close down the match saw the Stormers getting within two points of the hosts.
The Stormers struck the final demoralising blow when a darting Habana scored his side's only try of the match.
Deon Fourie forced a turn-over at the breakdown and the ball was spread wide to flanker and man of the match Siya Kolisi who sent a well weighted pass into the hands of a flying Habana.
With Grant succeeding with the conversion the Stormers were in a commanding position to cement their place at the top of the South African conference log.
The Bulls tried in vain to wrestle the lead back and left thousands of pink clad Bulls fans disappointed.
Final Score Bulls 14 (11) Stormers 19 (9)
Tries - P Spies
Pen - M Steyn 3
Tries - B Habana
Pen - P Grant 4
Con - P Grant
Cards - Frans Malherbe (59th min Yellow)
Referee: Jonathan Kaplan
Assistant Ref 1:Mark Lawrence
Assistant Ref 2:Cobus Wessels
TMO : Shaun Veldsman
Zane Kirchner, Akona Ndungane, JJ Engelbrecht, Wynand Olivier, Bjorn Basson, Morne Steyn, Francois Hougaard, Pierre Spies (captain), CJ Stander, Dewald Potgieter, Juandre Kruger, Flip van der Merwe, Werner Kruger, Chiliboy Ralepelle, Dean Greyling.
Replacements: Willie Wepener, Rayno Gerber, Wilhelm Steenkamp, Arno Botha, Jano Vermaak, Louis Fouche, Francois Venter.
Gio Aplon, Gerhard van den Heever, Juan de Jongh, Jean de Villiers (c), Bryan Habana, Peter Grant, Dewaldt Duvenage, Jebb Sinclair, Rynhardt Elstadt, Siya Kolisi, De Kock Steenkamp, Eben Etzebeth, Frans Malherbe, Tiaan Liebenberg, Deon Carstens
Replacements: Deon Fourie, Brok Harris, Quinn Roux, Don Armand, Nick Fenton-Wells, Louis Schreuder, Burton Francis.