A one-piece mold element (3, 7) for a mold (1) for manufacturing containers from blanks of plastic material by blow molding or stretch blow molding. The mold element (3, 7) includes a one-piece molding wall (4, 8) having a raised molding surface (5, 9) bearing the imprint of at least one portion of a container, the molding wall (4, 8) having at least one decompression vent (20) extending therethrough, the hole leading, via an inner opening (21), onto the molding surface (9), which is provided in the form of a slot.