St. Patrick's Athletic 0 Derry City 1
An Owen Morrison consigned Pat's to a first defeat of the season as Derry leapfrogged them to the top of the Premier Division table.
The win was no more than Derry deserved even if it stemmed from a dreadful mistake by Saints' keeper Brendan Clarke on 65 minutes.
Way off his line near the corner flag, Clarke's clearance fell straight to the Derry midfielder who fired the ball to the net.
Derry started well with Clarke having to make a superb sixth minute save from Clive Delaney's flick.
But Saints blew the best chance of the first half when skipper Jamie Harris put a free head from Keith Fahey's delivery wide.