Josh Benson struck in the third minute of stoppage time as League One Barnsley claimed a 1-0 win at the Riverside to dump Championship Middlesbrough out of the Carabao Cup.
Benson, who was a second-half substitute, slotted home the rebound after his own shot had been parried by Middlesbrough goalkeeper Liam Roberts.
Hayden Hackney fired a low first-half effort wide for the hosts, but Barnsley settled after a shaky start and went close themselves when Aiden Marsh wriggled free in the 18-yard box, only for his close-range strike to be saved by Boro debutant Liam Roberts.
Paddy McNair glanced a second-half header wide from a corner, but while Boro spent most of the second half pushing for a winner, substitute Daniel Dodds was denied by a sliding challenge from Robbie Cundy.
Dael Fry had the home side’s best late chance to secure a winner, but his goal-bound header from Caolan Boyd-Munce’s cross was tipped over by Walton.
And just as the game looked to be heading to penalties, Benson struck in injury-time to ensure Barnsley were able to celebrate a cup shock.
