If one firm buys inputs from a competitor, the input price may be used to internalize the competition between the firms. Thus, positive unilateral pricing effects may arise if one firm starts to buy inputs from a competitor. Conversely, unilateral pricing effects may be small if two firms with vertical relations merge, as pre-merger competition is partly internalized through the input price. We present a method for adjusting the formula of Hausman et al. (Econ Lett 111(2):119–121, 2011), in order to predict correct unilateral pricing effects not only for horizontal mergers, but also for structural changes in markets where one firm sells inputs to a rival.