Coupled spin and reaction dynamics of spin-correlated radical pairs is often described by a master equation due to Haberkorn. In a recent paper it was claimed that this equation is inconsistent with a description by a sum of individual quantum trajectories. The apparent inconsistency arises from an incorrect description of reaction attempts in the trajectory simulations. Results from quantum trajectory and Haberkorn master equation simulations coincide if these attempts are correctly described as quantum measurements of the spin state that happen on encounter of the two radicals. (C) 2016 Elsevier B.V. All rights reserved.