The title compound, C(12)H(14)O(3), is a natural product derived from the medium-sized hawthorn Crataegus persimilis ('prunifolia'). The mean plane of the butene moiety is twisted by 13.27 (7)° with respect to the that of the dioxobenzaldehyde moiety. There is an intra-molecular hydrogen bond between the hydroxyl group and the carbonyl O atom.