Callum Flatman scored the only goal as Kelty Hearts stunned Hibernian in the Premier Sports Cup.
The 20-year-old centre-half met a corner kick from former Easter Road favourite Scott Allan to head home on 58 minutes.
The League One hosts had to withstand a flurry of attacks from the Premiership side but held on for a famous victory.
Hibs, who made six starting changes from Tuesday's win over Queen's Park, hit the post either side of Flatman's header, through Martin Boyle and Dylan Vente.
A goal line clearance from Kanayo Megwa had prevented Kelty Hearts taking a first-half lead.
Hibs still lead Group C after playing three of their four games, two points clear of Kelty, who have played twice.