Callum Black marked his 100th Ulster appearance with a try as the Irish province reclaimed top spot in the Pro12 table on Friday with a narrow 13-10 victory over Glasgow Warriors.
Ulster were out-scored by two tries to one at the Kingspan Stadium, Lee Jones and Taqele Naiyaravoro crossing for the visitors in either half.
However, Black's converted touchdown and penalties from Ruan Pienaar and Paddy Jackson ensured Ulster's good form continued, with Naiyaravoro's late score only enough to earn Glasgow a losing bonus point.
There was a similarly tight tussle in south Wales, where a 76th-minute penalty from Aled Thomas earned Scarlets a 22-21 victory over Edinburgh.
Thomas split the posts for a fourth time after tries from Cornell du Preez and Alex Toolis had ensured Edinburgh came from 13 points behind to lead.
Scarlets sit fourth, but are only a point behind Ulster and Connacht.
While Ulster and the Scarlets claimed slender wins, Leinster racked up eight tries in a 52-0 thrashing of Zebre.
Eight different players crossed the whitewash for Leinster, who are now unbeaten in 10 league games at the RDS, including man of the match Garry Ringrose.