Package material blank comprising a multilayer material structure having a layer of cellulosic material and one or more layers of plastic laminate, the package material blank comprising: - a body panel having a main panel, two side panels arranged on different sides adjacent to the main panel and at least one third panel, arranged adjacent to one of the side panels; - end closure panels arranged adjacent to the body panel, the end closure panels comprising a top and bottom closure panels arranged adjacent to the main and the at least one third panel, respectively and flap closure panels arranged adjacent to the two side panels; - respective lines of weakness between each panel of the body and end closure panels for folding the panels along said lines of weakness; - a line of weakness on the main panel having a first portion and a second portion, wherein the first portion extends from a first point to a second point and the second portion extend from a third point to the second point; and characterized by further comprising an opening device having: - a tab arranged on a first surface of the blank - an elongated opening strip arranged on a second surface opposite the first surface, wherein - the tab is connected to the opening strip portion via a bridge penetrating through the multilayer material structure in a weakened area, the weakened area comprising a reduced thickness compared to a surrounding area of the package laminate structure, and - the opening strip is substantially parallel to the line of weakness between the main panel and the top closure panel. - a body panel having a main panel, two side panels arranged on different sides adjacent to the main panel and at least one third panel, arranged adjacent to one of the side panels; - end closure panels arranged adjacent to the body panel, the end closure panels comprising a top and bottom closure panels arranged adjacent to the main and the at least one third panel, respectively and flap closure panels arranged adjacent to the two side panels; - respective lines of weakness between each panel of the body and end closure panels for folding the panels along said lines of weakness; - a line of weakness on the main panel having a first portion and a second portion, wherein the first portion extends from a first point to a second point and the second portion extend from a third point to the second point; and - a tab arranged on a first surface of the blank - an elongated opening strip arranged on a second surface opposite the first surface, wherein - the tab is connected to the opening strip portion via a bridge penetrating through the multilayer material structure in a weakened area, the weakened area comprising a reduced thickness compared to a surrounding area of the package laminate structure, and - the opening strip is substantially parallel to the line of weakness between the main panel and the top closure panel. - the tab is connected to the opening strip portion via a bridge penetrating through the multilayer material structure in a weakened area, the weakened area comprising a reduced thickness compared to a surrounding area of the package laminate structure, and - the opening strip is substantially parallel to the line of weakness between the main panel and the top closure panel.