Saracens (11) 24
Try: Ratuvou, Chesney
Pens: Jackson (4)
Cons: Jackson
Gloucester (13) 22
Try: Brown
Pens: Mercier (5)
Cons: Mercier
Kris Chesney's late converted try ensured Saracens made it six home wins in a row with the game's final kick.
Dan Scarbrogh set up Kameli Ratuvou to open the scoring for the home side, before lock Alex Brown touched down on Gloucester's first serious attack.
Glen Jackson and Ludovic Mercier traded second-half kicks as the packs took over, and Andy Farrell ended up in the scrum when Fabio Ongaro was sin-binned.
But at the death, Chesney scored and Jackson's kick sealed the points.
"We deserved it. We made lots of errors and gave away lots of penalties and you can't do that at this level.
"We showed ambition at the end and had courage to keep playing when we could have accepted a losing bonus point.
"Regarding the referee, there are quite a few moments that we could discuss if we wanted to. His decision at the end is irrelevant as far as I'm concerned."
"They knocked on, we kicked the ball into touch and the referee marched us back for a line-out to them just outside our own 22.
"He said he called 'advantage over' but I don't believe it. It's another to add to the mysteries of refereeing.
"This is one of the most pivotal games of our season and it has been decided by a referee's decision."
Saracens: Scarbrough, Vedia, Sorrell, Farrell, Ratuvou, Jackson, Kock; Yates, Ongaro, Johnston, Chesney, Fullarton, Raiwalui, Hill, Skirving.
Replacements: Cairns, Mercey, Ryder, Gustard, Dickens, Powell, Penney.
Gloucester: Morgan; Bailey, Keil, Allen, Foster, Mercier, Lawson; Califano, Azam, Nieto, James, Brown, Buxton, Hazell, Forrester.
Replacements: Davies, Wood, Bortolami, Boer, Richards, Adams, Goodridge.