The Recreation Park side clinched the title in style last weekend with an 8-1 win over Elgin, but their trip to Berwick resulted in a 5-0 defeat.
Hibs’ on-loan Danny Handling opened the scoring on 13 minutes with Lee Currie adding a second just 60 seconds later.
An own goal from Ryan Harding made it three before half-time with Handling and Stuart Noble completing the scoring. Berwick boss Ian Little said: “That was the best performance I have seen in my time as manager.”
Alloa manager Paul Hartley, who changed his line-up to give fringe players a chance to impress said: “We just didn’t perform. I do not want to take anything away from Berwick, but in hindsight I shouldn’t have made the changes.”
Second-placed Stranraer, who have already qualified for the play-offs, lost 3-0 to Peterhead with Rory McAllister scoring either side of half-time and Roy McBain adding a third.
Queen’s Park, who still need a point to be sure of extending their season, lost 3-1 at Montrose despite Tony Quinn giving them an early lead. Sean Crighton levelled before the break with Martin Boyle and Jamie Winter scoring in the second. Fifth-placed Annan kept their play-off chances alive by defeating Elgin City. Paul Millar put Elgin in front before Jordan McKechnie and Graeme Bell scored to seal the win.
Finally, Clyde defeated East Stirlingshire 1-0 thanks to John Neil’s goal.