A second-half try from Gio Aplon proved enough for the Stormers to beat the Cheetahs 13-6 in a wet Bloemfontein on Saturday.
A bonus-point win for the Stormers would have seen them move above the Chiefs at the top of the overall standings. But the team from Cape Town have failed to pick up a single four-try bonus point all season and the meteorological conditions at the Free State Stadium didn't offer any help as the cold rain drove down onto a soggy pitch.
The result does however ensure that the Stormers will finish at the summit of the South African conference and a single point against the Rebels next week will guarantee a home semi-final.
A dour first half characterised by handling errors and territorial kicking came to an end (at last) with the scores locked at 3-3.
It took 17 minutes for the first points to be scored via the boot of Stormers fly-half Peter Grant. The visitors had come close to crossing the whitewash once but when a pile of orange jerseys prevented Deon Fourie from releasing just inches short of the line, Grant could step up and open his account.
The Cheetahs had their first chance at points in the 34th minute thanks to a scrum penalty but Riaan Smit sent his effort wide. The home fly-half found the mark just before half time however to level the scores after a period of sustained pressure from the hosts.
The Stormers started the second period clearly pushing for a try and turned down a shot at goal three times in favour of going for an elusive five-pointer.
But even when the Cheetahs were reduced to 14 men - Willie le Roux saw yellow for a cynical offside - the home defence could not be breached and eventually the Stormers took three, again from Grant.
Smit levelled the scores again almost immediately afterwards but the deadlock would soon be broken. Grant spotted space behind the Cheetahs' defence and lobbed a perfectly-weighted kick in the corner. The chasing Aplon simply had to collect the ball after a favourable bounce to ghost over untouched.
Grant added the extras with an excellent kick from out wide to put the Stormers ahead 13-6 approaching the hour mark and the scorers weren't troubled again.
Pens: Smit 2
Pens: Grant 2
Yellow card: Le Roux (Cheetahs - 45th min - deliberate offside)
Cheetahs: 15 Willie le Roux, 14 Philip Snyman, 13 Robert Ebersohn, 12 Barry Geel, 11 Cameron Jacobs, 10 Riaan Smit, 9 Piet van Zyl, 8 Justin Downey, 7 Pieter Labuschagne, 6 Heinrich BrÃ¼ssow, 5 Izak van der Westhuizen, 4 Andries Ferreira/George Earle, 3 Marcel van der Merwe, 2 Adriaan Strauss (c), 1 Trevor Nyakane.
Replacements:16 Hercu Liebenberg, 17 WP Nel, 18 George Earle/Waltie Vermeulen, 19 Ashley Johnson, 20 Tewis de Bruyn, 21 Sias Ebersohn, 22 Nico Scheepers.
Stormers: 15 Joe Pietersen, 14 Gio Aplon, 13 Juan de Jongh, 12 Jean de Villiers (c), 11 Bryan Habana, 10 Peter Grant, 9 Dewaldt Duvenage, 8 Jebb Sinclair, 7 Rynhardt Elstadt, 6 Siya Kolisi, 5 Andries Bekker, 4 De Kock Steenkamp, 3 Frans Malherbe, 2 Deon Fourie, 1 Steven Kitshoff.
Replacements: 16 Tiaan Liebenberg, 17 Deon Carstens, 18 Quinn Roux, 19 Don Armand, 20 Louis Schreuder, 21 Burton Francis, 22 Gerhard van den Heever.
Referee: Marius Jonker (South Africa)