Colchester United were on the wrong end of an FA Cup upset after they were beaten at home by National League South side Oxford City.
Matt Paterson's second-half header was enough for Oxford to progress against a team two divisions higher than them in the football pyramid.
It's only the second time that Oxford have reached the second round in their history, while Colchester will be counting the cost of missing out on a potentially lucrative cup run.
Elsewhere, Peterborough United are still in the hat for round two but they will have to replay their game against Conference outfit Tranmere Rovers.
Posh had led through Jack Marriott's opener at the ABAX Stadium, but substitute Andy Cook equalised with 20 minutes remaining to force a 1-1 draw.
Northampton Town were also taken to a replay by fellow League One side Scunthorpe United, while Stevenage were 5-0 winners over part-timers Nantwich Town with Matt Godden helping himself to a hat-trick.
Essex clubs Chelmsford City and Southend United were knocked out by Gateshead and Yeovil Town respectively, but Luton Town did manage to pull off a shock by beating Portsmouth 1-0 at Kenilworth Road courtesy of a James Collins strike.
FA Cup first round results
- Colchester United 0-1 Oxford City
- Gateshead 2-0 Chelmsford City
- Luton Town 1-0 Portsmouth
- Northampton Town 0-0 Scunthorpe United
- Peterborough United 1-1 Tranmere Rovers
- Stevenage 5-0 Nantwich Town
- Yeovil Town 1-0 Southend United