Reading's unbeaten 15-match home run came to an end when they lost 1-0 to Bristol City in a hard-fought Sky Bet Championship contest at the Madejski.
Although Reading dominated much of the game, they could not get past agile City goalkeeper Frank Fielding, who made several good saves.
City showed in attack only in patches but clinched victory in the 84th minute when centre back Aden Flint drove in from 10 yards out.
Reading, undefeated at home in all competitions since losing 1-0 to QPR in the league in January, had signed off for the international break with a 2-0 win at Birmingham.
Sone Aluko, the forward signed for a club record B#7.5million from Fulham last month, made his debut for Jaap Stam's side.
City had only one victory in their opening five Championship matches but had drawn three in a row before making the short trip up the M4 to Berkshire.
Yet they began promisingly, with Famara Diedhiou having a chance from a 25-yard free-kick - only to send it too high.
Reading replied with an excellent deep cross from Modou Barrow, which flew over Fielding, but there was no one on hand to touch it in at the far post.
Bobby Reid volleyed over from a Callum O'Dowda cross as City pushed forward again, but Reading were quick to up the tempo.
Aluko, who had become increasingly influential, shot from distance but off target, then supplied a fine cross that Barrow sliced well wide.
Reading kept up the pressure and Liam Kelly struck a low 25-yard shot that forced an acrobatic save from Fielding.
Kelly was swiftly involved again but, after collecting an Aluko pass, shot tamely into the side-netting.
City defender Nathan Baker was perhaps fortunate to escape a red card when he brought down Barrow, who was galloping clear, but referee James Linington deemed it worthy only of yellow.
Reading started the brighter after the interval and, with thunder and lightning crackling overhead, Jon Dadi Bodvarsson somehow miscued a Barrow cross from six yards out.
Leandro Bacuna's 20-yard effort was well saved by Fielding before City were afforded some respite when Reid broke away to set up Jamie Paterson, who flashed a shot wide.
Bodvarsson astonishly again miscued with the goal gaping, this time from an Aluko cross, and City snatched the winner six minutes from time.
Reading had several chances to clear the ball but failed to do so, allowing Flint to pounce with a clean strike.
Home keeper Vito Mannone got a hand to it but could not prevent it from trickling over the line.