For closing packages (9) provided with a movable pouring spout, an adhesive is applied to one or both portions of a first pair of folding portions (16) which are movable integrally with an inclined wall (14) of a chamfered corner (10) of the package (9). The first folding portions (16) may be coupled to a second pair of folding portions (18), which are movable integrally with an oscillatable tongue (12) of the spout. The adhesive adheres the second portions (18) to the first portions (16) when the tongue (12) moves toward the inclined wall (14).