A blank for forming a packaging container, the blank comprising: a sheet defining an internal side and an external side of the packaging container; wherein the sheet comprises: a plurality of side panels separated from one another by side crease lines; a plurality of flaps, each one of the flaps extending from one of the side panels and being joined to the respective side panel by a flap crease line, each pair of adjacent flaps forming an inner flap and an outer flap; a sealant film disposed on the internal side of the sheet and having areas which are bonded to a portion of each one of the side panels and to a portion of each one of the flaps; wherein the sealant film comprises an unbonded area between the areas bonded to adjacent inner and outer flaps to allow the inner flap to first be folded inwards before the outer flap is folded onto the inner flap to form an end panel of the packaging container, with the sealant film forming a seal between the flaps.