In the crystal, mol-ecules of the title compound, C(11)H(10)N(2)S, are connected by C-H⋯N inter-actions around threefold axes. Furthermore, they form stacks along the c axis showing π-π inter-actions between pyrimidine rings [centroid-centroid distance = 3.721 (1) Å]. The central ring is essentially planar with an r.m.s. deviation of 0.007 Å. The five-membered ring adopts an envelope conformation with the flap atom deviating by 0.241 (4) Å from the mean plane (r.m.s. deviation = 0.002 Å) through the other four ring atoms.