The title compound, C(13)H(12)O(2)S(2), belonging to the group of dioxoketene cyclic S,S-acetals, was prepared from the corresponding dione in high yield. In the structure, the C=O and C=C bonds are not coplanar, with O=C-C=C torsion angles of -36.8 (4) and -21.0 (4)°. The dithian ring has a twisted conformation.