Glasgow eked out a narrow victory over Scarlets at a rain-soaked Scotstoun to secure a home tie in the URC quarter-finals.
Dan Jones kicked Scarlets into a 6-0 lead before Sione Vailanu powered over to make it a one-point game at the break.
Jones struck again from the tee but substitute Fraser Brown's try was enough to see Glasgow home.
It stretches Warriors' winning streak to six matches in all competitions.
Munster could still catch Glasgow on points, but would be unable to overhaul the Scots' tally of wins.
An intriguing subplot to this match is the fact these sides will meet again in two weeks' time in the semi-final of the European Challenge Cup. The number of changes on both sides perhaps diminished any potential psychological blow to be struck, but the knowledge that they could guarantee a home URC quarter-final would have been motivation enough for the home side.
Ryan Wilson led his side out in the week it was announced that Warriors' second-highest appearance-maker would be leaving the club at the end of the season.
His side found themselves immediately on the back foot, bungling receipt of the opening kick-off and after several minutes of pressure, Jones banged over a penalty to get Scarlets up and running.
A smart break from the base of the scrum from Kieran Hardy had the Warriors defence scrambling and when Jones was given another shot at goal, this time from further out, he again did the business from the tee.
As the heavens opened and ball-handling conditions deteriorated, that 6-0 lead looked handy enough. The wet ball made attacking rugby problematic and so Glasgow had to take a more direct route to get back into the match.
A rolling line-out maul was veering towards the line before Vailanu peeled off the back and blasted his way through a couple of tackles to get over the line and bring Glasgow back within one going into the break.
Wilson departed the scene to a fantastic ovation early in the second half on what could be his final appearance at Scotstoun after 13 years of sterling service.
There was little else to get the crowd on their feet with the ball hitting the deck all over the place.
Jones knocked over another penalty to give Scarlets a four-point lead, but Glasgow once again deployed the line-out maul to great effect, substitute hooker Brown grounding, and Tom Jordan converting, to put the Warriors in front for the first time in the match.
Glasgow had wrestled control of the match but an inability to keep hold of the ball spoiled their chances to put some daylight on the scoreboard.
Scarlets looked to have caught Warriors napping when Morgan Jones snaffled the ball at the base of the ruck and streaked away from his own 22 to score, but the try was ruled out after replays showed the lock had gathered the ball from an offside position.
Sighs of relief around Scotstoun after an ugly but hard-earned win. Let's hope for a dry ball, and a better spectacle, when these sides meet later in the month for a place in a European final.
Glasgow: Huw Jones; Kyle Steyn (capt), Stafford McDowall, Sam Johnson, Cole Forbes; Tom Jordan, Ali Price; Jamie Bhatti, Johnny Matthews, Zander Fagerson, Lewis Bean, JP du Preez, Ryan Wilson, Matt Fagerson, Sione Vailanu.
Replacements: Fraser Brown, Nathan McBeth, Simon Berghan, Richie Gray, Scott Cummings, Rory Darge, Jamie Dobie, Domingo Miotti.
Scarlets: Tom Rogers; Steff Evans, Ioan Nicholas, Eddie James, Ryan Conbeer; Dan Jones, Kieran Hardy; Wyn Jones, Shaun Evans, Sam Wainwright, Morgan Jones, Vaea Fifita, Iwan Shenton, Josh Macleod (capt), Carwyn Tuipulotu.
Replacements: Daf Hughes, Steff Thomas, Javan Sebastian, Aaron Shingler, Iestyn Rees, Dane Blacker, Rhys Patchell, Joe Roberts.