The Stormers have edged the Bulls 20-17 in the battle for top spot in Super Rugby, and in the South African conference.
Peter Grant kicked a 77th-minute penalty to finally separate the north-south rivals and hold off a second-half surge from the Bulls, who came back from 14-0 down at the break to tie it at 17-17 in a bone-crunching derby at Newlands.
The Stormers remain the only unbeaten team in the Super Rugby championship.
A fired-up Western Force showed little sympathy for an injury-ravaged Queensland Reds team as they thrashed the visiting champions 45-19 in Perth on Saturday.
The Sharks beat the ACT Brumbies 29-26 in Canberra
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