A 90th-minute strike from Alex Teniola cost Maidstone their unbeaten start to the Ryman League Premier Division season at Tonbridge on Bank Holiday Monday.
Teniola found the bottom corner from the edge of the area after Flavio Tavares was gifted space to work an opening for his Angels team-mate.
Rarely did United look like extending their winning start to six matches but with Angels largely restricted to shots from distance, they hadn't looked like losing either.
Angels worked hard for new boss Steve McKimm without troubling Lee Worgan in a quiet first half that saw the best chance fall to United's Collin.
He latched on to a superb through ball from James Rogers after Tonbridge free-kick appeals were turned down but dragged his strike wide after bearing down on goal.
Jack Parkinson might have made more of a far-post header from a Matt Bodkin corner while Angels' best effort saw Teniola drive a 30-yard free-kick just wide.
Stones missed the presence of the injured Jay May in attack, with former United defender Jerrome Sobers keeping Ashley Miller quiet.
But the visitors looked the more dangerous side as the second half wore on,with Alex Flisher seeing more and more of the ball down the left.
He almost forced an own goal from Ben King after thrashing a ball across the goalmouth, then fired wide after collecting Parkinson's crossfield free-kick.
Flisher also sent in a cross that went inches over Ben Greenhalgh's head when well placed.
Tonbridge had pace on the break all afternoon but it was hard to see them scoring until the ball arrived at Teniola's feet in the last minute.
United remain second in the table but have fallen three points behind leaders Margate, who won 5-1 at Lewes.
Angels are 10th after maintaining their 100% home record.
Tonbridge: Merson, Parter, King, Carey, Sobers, Parkinson, Folkes (Slocombe 79mins), Teniola, Medlock (Tweddle 89mins), Whitnell (Tavares 86mins), Okojie. Sub not used: Bolagi.
Maidstone: Worgan, Butcher, Mills, Coyle, Miles, Rogers (Brown 79mins), Bodkin (Watt 87mins), Parkinson, Miller (Greenhalgh 63mins), Collin, Flisher. Subs not used: Robertson, Godmon.