The invention relates to a method of manufacturing a heat-sealable packaging material, the method comprising the steps of: providing a paperboard substrate comprising a top ply, applying a first dispersion barrier layer on the top ply, wherein the first dispersion barrier layer comprises a latex having a first glass transition temperature, and applying a second dispersion barrier layer on the first barrier layer, wherein the second dispersion barrier layer comprises a latex having a second glass transition temperature, wherein the second glass transition temperature is higher than the first glass transition temperature, wherein the grammage of the second dispersion barrier layer is lower than the grammage of the first dispersion barrier layer, and wherein the second dispersion barrier layer comprises pigments. The invention further relates to a respective heat-sealable packaging material.