Nat. Chem. Biol. 11, 141–147 (2015); published online 5 January 2015; corrected after print 15 July 2015

In the version of this article initially published, the zymosterol and zymostenol structures shown in Figure 3a were depicted with a double bond at C14-C15, where there should have been a single bond. The error has been corrected in the HTML and PDF versions of the article.