A method of manufacturing a film having an oxygen transmission rate (OTR) value in the range of 0.1 to 200 cc/m2*24 h at 23° C., 50% relative humidity (RH), and an OTR value in the range of 0.1 to 2000 cc/m2*24 h at 38° C. at 85% RH, comprising at least 60% by weight nanocellulose based on the weight of the total amount of fibers in the film, wherein the method comprises the steps of, providing an aqueous suspension comprising said nanocellulose; forming a web from said aqueous suspension; calendering said web at a line load of at least 40 kN/m, and at a temperature of at least 60° C. wherein said film is formed and said web has an OTR value in the range of 50 to 10 000 cc/m2*24 h at 23° C., 50% RH before said calendering step, or more preferably in the range of 500 to 5000 cc/m2*24 h at 23° C., 50% RH before said calendering step.