A gasket is for an annular compact flange. The compact flange includes two joinable flange halves which are formed with contact surfaces facing each other, and at least one of the flange halves having an axial, centric bore. An annular gasket groove is arranged in each of the flange halves, which is arranged to sealingly receive a common gasket. The gasket groove has a proximal side and a distal side relative to the bore, the distal side, which is conical, forming a groove sealing surface against the gasket. The gasket, which seals at the groove sealing surface, is formed with a plate portion positioned between the contact surfaces.