Replying to: C. M. Gaskell , 10.1038/nature08665 (2010) Gaskell1 makes the point that the profile of the Balmer lines in the candidate binary supermassive black hole2 AGN J1536+0441 bears some similarity to those that are thought to arise from disk emission in other objects. He further argues that two predictions of the competing binary black-hole hypothesis are (1) radial velocity changes that are interpretable in terms of the binary orbit, and (2) line fluxes in the two peaks that vary independently.