In this Letter, we ought to have cited four relevant references. The first two1,2, published after submission of the first version of our manuscript, report a cultivar-dependent reduction in wheat grain quality under elevated carbon dioxide (CO 2 ) in an Australian Grains Free-Air Carbon dioxide Enrichment (AGFACE) experiment. A subset of these results was reported in two papers published in 2012 (refs. 3,4). Although our work was independent of these papers, we regret not citing them to highlight their relevance. The original Letter has not been corrected.