The problem of flame propagation through a spatially periodic shear flow is revisited. When the flow intensity exceeds a certain critical level the corrugated flame either quenches or transitions to detonation. The quenching takes place for relatively small-scale flows where the impact of the flame stretch is strong. In large-scale flows the stretch weakens, while the impact of precompression increases, and the flame transitions to detonation, provided the flow intensity is high enough. In the parametric space a change of the dynamical picture occurs in an abrupt nearly jumpwise manner. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.