Alex Revell returned to haunt his former club as Leyton Orient knocked Swindon out of the Carling Cup with a 2-1 win.
Jon-Paul McGovern had given Swindon a first-half lead but goals from Ryan Jarvis and Revell, who left the County Ground in the summer, put Russell Slade's men through.
McGovern put Danny Wilson's men in front after 35 minutes, steering home after some good work from David Ball.
Swindon nearly made it two but Charlie Austin could not convert Ball's cross before the latter shot narrowly wide just after the break.
That signalled the start of Orient's revival and Jarvis got them level after 67 minutes, beating the offside trap to collect Matthew Spring's pass and score.
Five minutes later Revell took centre stage, drilling a 20-yard free-kick low into the corner after Stephen Dawson had been fouled.