Nat. Chem. Biol. 10, 1043–1048 (2014); published online 26 October 2014; corrected after print 29 January 2015

In the version of this article initially published, the chemical structures of the two cyclic dinucleotides in Figure 4a were incorrect at the triphosphate group, with each of the phosphates shown as containing two extra hydrogen atoms. The error has been corrected in the HTML and PDF versions of the article.