Stade Francais put aside last month's merger fiasco and a red card to down Ospreys 25-21 on Sunday and seal a place in the European Challenge Cup semi-finals.
The 2015 French Top 14 champions will face Bath at home three weeks from now after narrowly negotiating their quarter-final at the Principality Stadium in Cardiff.
Stade went into the break leading 8-6 after Georgian prop Zurabi Zhvania's try.
Ospreys took control briefly at 14-11 as Stade winger Josaia Raisuqe was sent off in the 51st minute for a second yellow card offence.
But the French visitors came good with tries from wing Julien Arias and substitute back-row forward Raphael Lakafia.
Fly-half Jules Plisson contributed two penalties and two conversions.
This was a welcome result for the Parisian side following their torrid March when shock plans to merge the club with Racing 92 were scrapped after sparking outrage from top internationals, fans and officials.
Stade's players went on strike in protest.
Up against them in the semi-final are Bath who booked their semi-final spot with a 34-20 home defeat of another Top 14 side, Brive, on Saturday.
The other semi of Europe's second-tier competition sees Top 14 leaders La Rochelle, 32-22 winners at Edinburgh on Friday, face Gloucester, who defeated Cardiff Blues 46-26.
The semi-finals are scheduled for April 21-23, with the final in Edinburgh on May 12.