2,3-Diaminopyridinium hydrogen malonate

In the title molecular salt, C5H8N3+·C3H3O4 , the cation is essentially planar, with a maximum deviation of 0.005 (1) for all non-H atoms. In the anion, an intramolecular O—H...O hydrogen bond generates an S(6) ring. In the crystal, the cations and anions are connected via N—H...O hydrogen bonds and a weak C—H...O interaction, forming layers parallel to the ab plane.