The Ospreys made hard work of their 14th straight win over Welsh opposition as Newport Gwent Dragons were defeated 20-10 at the Millennium Stadium.
It keeps the Ospreys play-off chances alive but it could have been far more comfortable had they been disciplined in the first half and turned huge pressure into points.
But it was only in the final 20 minutes that the Liberty Stadium men put the seal on the game.
To get to that outcome, the Dragons' try came via scrum-half Richie Rees, with Kris Burton converting and wing Tom Prydie landing a long-range penalty.
The Ospreys' points came via a penalty try and a touchdown for scrum-half Tom Habberfield, while fly-half Dan Biggar converted both and also landed two penalties.
At either end of the match, the Ospreys were dominant and twice in the first 14 minutes were denied tries when full-back Richard Fussell's effort was scrubbed for an earlier knock on, while number eight Dan Baker knocked on in the action of touching down.
Indeed, the Ospreys had so much possession and territory, they should have been running away with it but were frustrated by indiscipline at the loose situations within metres of the Dragons' line, where they were repeatedly penalised and lost the ball to turnovers.
Ospreys' Welsh international Ryan Jones, at lock, was sin-binned for killing the ball at a ruck five metres from his line but the Dragons could not take advantage as the match was remarkably left scoreless at half-time.
That first half of defiance by the Dragons had an immediate positive impact as they broke the deadlock within six minutes of the restart with a superbly worked try that Burton converted.
Rees started and finished the move on the right that involved full-back Hallam Amos, centre Tyler Morgan and lock Cory Hill before the scrum-half dashed in from 15 metres.
But the Ospreys hit back when replacement flanker Nic Cudd high-tackled Biggar and was sent to the sin-bin, leaving the Welsh international fly-half a 38-metre penalty chance that he took.
The game began to open up further as the Ospreys mounted another attack and, this time, made no mistake on the Dragons line as Habberfield dived over from two metres for a try that Biggar converted.
A silly error by centre Jonathan Spratt, where he put his arm up in midfield and deflected the ball while in an offside position, earned him a yellow card and saw Prydie land a 38-metre penalty to level the match.
Finally, the Ospreys went in front when Biggar booted a 40-metre penalty as they put down the hammer again, forcing Morgan to infringe and get a yellow card before a scrum on the Dragons line was collapsed, leaving referee Nigel Owens no option but to award a penalty try.
Fussell was again left without a try when he knocked on over the line in the second but it would only have been a gloss-adding score.