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Agnes Grudniewicz and colleagues argue for a definition of a predatory journal that will protect scholarship (Nature576, 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.