The invention relates to a lamp comprising a lamp bulb (2) and a lamp base (3), which lamp base (3) comprises a projection (4) located in a substantially central position of the lamp base (3) and extending in a direction away from the lamp bulb (2), at least one lock-engaging portion (6), and a substantially flat base surface (5) opposed to the lamp bulb (2) and surrounding the projection (4), characterized in that the at least one lock-engaging portion (6) is located on the edge of the base surface (5) surrounding the projection (4) remote from the central projection. The invention also relates to a lampholder (10) for cooperation with the lamp (1) according the invention, the lampholder (10) comprising an aperture (12) in a substantially central position of the lampholder (10), at least one counter lock-engaging portion (15), and a substantially flat holder surface (11) surrounding the aperture, characterized in that the at least one counter lock-engaging portion (15) is located on the edge of the holder surface (11) surrounding the aperture (12) remote from the central aperture (12).