In the title co-crystal, C7H4N2O6·C6H7NO, the two components are linked by an intermolecular hydrogen bond between the O—H and N—O groups [O⋯O 2.487 (1) Å]. The dihedral angle formed by the planes of the rings of the component mol­ecules is 7.40 (7)°. The rings of the complex are stacked along the b axis of the crystal. The stacks exhibit overlap between the aromatic rings, with a mean interplanar distance of 3.136 (1) Å.