Agnes Grudniewicz and colleagues argue for a definition of a predatory journal that will protect scholarship (Nature 576, 210–212; 2019). Their proposed definition excludes an important feature of predatory journals — poor-quality peer review — on the grounds that such reviews are not accessible for analysis. It is a sad irony that this lack of transparency — a tell-tale trait of predatory journals — should be used to justify omitting an assessment of peer-review quality.

If misuse of the peer-review label is not included in the definition of predatory journals, it could strengthen rather than weaken them. Formal listings of those journals might shrink under such a definition: many journals would be removed because their questionable peer-review procedures have escaped scrutiny and they seem otherwise respectable. They could then become attractive outlets to potential authors.

As Grudniewicz and colleagues point out, legitimate journals that keep their peer-review processes under wraps encourage predatory practices. If publication of signed referees’ comments were standard, journals publishing unrefereed papers would quickly be exposed. In our view, therefore, open peer review should be compulsory and the definition of predatory journals should include the quality of peer review.