Derry City moved top of the Premier Division with a 1-0 victory over Waterford at the RSC.
Ben Doherty's second-half header gave the visitors an unexpected lead after Waterford goalkeeper Louis Jones fumbled a routine catch over the goal line.
The home side came agonisingly close to a late equaliser as substitute Gbemi Arubi's rebound found the back of the net but the forward was flagged for offside.
An uneventful first half hour in Waterford was sparked into life after 35 minutes when Derry's Adam O'Reilly played Paul McMullan through down the right, but the midfielder's strong effort was denied by the post.
Waterford's best chance of the half came on the stroke of half-time when Samuel Glenfield's acrobatic effort was blocked in the box before Darragh Leahy's rebound was excellently saved by an alert Brian Maher. Padraig Amond's close-range follow-up was subsequently blocked and cleared for a corner.
In the second half, the home side picked up where they left off and came inches away from an opener.
Amond produced a clever chest pass to Christie Pattisson who unleashed a terrific strike from outside the box which blasted off the right post, the same post that denied McMullan in the first half. Ryan Burke's darting follow-up strike rippled the side-netting of Maher's goal.
The visitors were gifted the lead on the hour mark after Jones fumbled a routine catch on the goal line from an unthreatening Doherty header. Jones appeared to reclaim the ball but the officials deemed the ball to have crossed the line.
Burke had a great opportunity to salvage a point in the 90th minute as the cross came in from Arubi to find the defender on the edge of the box but Burke's side-footed effort flew over the crossbar.
Waterford's frustrating night continued late into added time when the hosts had the ball in the back of Derry's net after a penalty area scramble fell to Arubi who netted but had already been flagged offside by the linesman.
The Candystripes make it four from four against Waterford this season, scoring eight without conceding a goal to the Blues.
Keith Long's side remain third after a frustrating night but now sit nine points off Derry at the top of the table.
Derry City Take Advantage of Shelbourne's Slip Up
The Candystripes' win at Waterford was their fourth in a row against the Blues, and it came thanks to a bizarre own goal by Waterford goalkeeper Louis Jones.
A Helping Hand From the Opposition Goalkeeper
Derry City's win over Waterford was a crucial one in the context of the title race. They are now top of the table, but they have a game in hand over their closest rivals Shelbourne.
Shelbourne have been in good form this season, but they have lost their last two games, giving Derry City an opportunity to move to the top of the table.
The game at Waterford was a tense affair, with both teams having chances to score. However, it was Jones's mistake that proved to be the difference between the two sides.
An Important Win for Derry City
The win over Waterford was a big boost for Derry City, who are now in a strong position to win the league title. They have a squad full of experienced players, and they are playing with a lot of confidence at the moment.
However, they will know that they need to keep winning games if they want to stay at the top of the table.
The race for the League of Ireland Premier Division title is wide open, with a number of teams still in contention. Derry City are in a strong position, but they cannot afford to slip up if they want to win their first title since 1997.