A transistor outline (TO) package including a header with at least one optoelectronic device. The header is bonded to a pot-shaped metal cap, which has a window that is transmissive to electromagnetic radiation, such that the at least one optoelectronic device is arranged in a hermetically sealed interior. The wall of the metal cap has at least one lateral wall portion and/or end wall portion which is thickened towards the interior compared to a portion of the lateral wall of the metal cap adjacent to the header.