Leroy Griffiths's poor penalty cost non-league Sutton as they lost to Notts County in the FA Cup second round.
The minnows were the better side early on and Griffiths and Harry Beautyman both forced saves from Stuart Nelson.
Jeff Hughes was eight yards out when he clipped home the opener from Karl Hawley's shot before Griffith's kick in first-half stoppage-time was saved.
Sutton's Karl Murray was sent off late on for two bookings before Hughes scored from close range in injury-time.
The Blue Square Bet South side's penalty had been awarded when Sam Sodje fouled Craig Watkins at the end of the first half.
Sutton were never outclassed by their Football League opponents but the game petered out in the second half and they never looked like scoring a late equaliser before Hughes's clincher.
Notts County will now visit Championship side Doncaster in the third round.