Northern Ireland Under-21s have slipped to their first defeat in Euro 2019 qualifying as Slovakia scored the only goal in Tuesday's match in Senica.
Ian Baraclough's charges had claimed last-gasp wins over Estonia and Albania in his first two matches in charge, leaving them on the verge of making history by winning three in a row.
However, NI - who had previously not won a game in four years - were undone by 19-year-old midfielder Laszlo Benes, who drilled a right-footed effort from 12 yards past Conor Mitchell just after the hour.
The 1-0 defeat for the visitors means that Slovakia take over from Northern Ireland on goal difference as Group Two leaders.
Northern Ireland's next match is at home to Estonia on October 10.